Characteristics of the main types of algae. lower plants or algae lower plants or algae

All heterokonts seem to have a flagellar apparatus. There are 2 flagella, and on one of them there are very characteristic tubular three-membered pinnate outgrowths, or hairs - mastigonemes. It was the presence of two unequal flagella that served as the basis for naming this vast group of aquatic organisms multiflagellatedalgae, or heterocontami. In addition to differences in length, the flagella also differ morphologically: the main flagellum consists of an axis and ciliated hairs pinnately located on it, the lateral flagellum is smooth and flagellated. The composition of pigments is also similar - chlorophylls a and With and numerous carotenoids, as well as the structure of chloroplasts. Chloroplasts are surrounded by four membranes, with the two outer membranes connected to the cell's endoplasmic reticulum.

As part of the Heterocont (Diversified) algae division, several groups of algae are united in the rank of classes: Brown, Golden, Yellow-green, Rafidophytes, Sinuraceae, Feotamnia, Eustigma, some were previously considered as independent divisions.

Class Brown algae– Phaeophyceae (Fucophyceae)

The name of the class "brown algae" reflects the color of their thallus (from the Greek. Rhaios- swarthy). The color is due to the presence of a large number of brown and yellow pigments - in addition to chlorophylls a and With and β -carotene in their chloroplasts there is an excess of xanthophylls, especially fucoxanthin.

Multicellular, predominantly large algae, especially widespread in the cold waters of both hemispheres. Neither unicellular nor colonial forms are known among brown algae. About 1.8 thousand species are known.

Cell structure. The cell in brown algae species is eukaryotic: it has formed organelles with its own membranes: the nucleus, mitochondria, plastids, etc. Green pigments are chlorophylls a and With- masked by additional ones: orange carotenes and yellow-brown xanthophylls; of the latter, fucoxanthin predominates. In the cells of brown algae, one to many plastids are found. On top of the outer cell membrane, brown algae cells usually develop a rigid cell wall.

The core is most often one, but sometimes there are several cores. In some representatives, as the age of the cell increases, the number of nuclei increases. There is always one nucleolus in the nucleus.

Chloroplasts of vegetative cells of brown algae have an eye (stigma) and pyrenoids, which can be one or more; some species lack pyrenoids. The ocellus, consisting of 30–40 lipid globules, functions as a lens that focuses light on the flagellar swelling, which is a photoreceptor. Zoospores and gametes of brown algae usually do not have an eye. Spare substances are deposited in pyrenoids. Chloroplasts are most often small, discoid, parietal. Their shape can be stellate, ribbon-like or lamellar. The shape of chloroplasts in brown algae cells can change as the cell ages. The chloroplast envelope consists of four membranes, with the two outer membranes connected to the EPS, the endoplasmic reticulum of the cell.

The cellulose that makes up the cell wall of brown algae - sometimes called algullose - differs in properties from the cellulose of higher plants. Outside of the cellulose wall is a highly mucilaginous pectin layer, formed mainly by alginic acid and its salts and compounds with protein substances. Alginic acid also found only in brown algae.

General characteristics.

All brown algae are phototrophs. Products of photosynthesis - specific carbohydrate chrysolaminarin,alcohol mannitol and lipids. Lipids accumulate in the form of oil droplets. Chrysolaminarin is deposited outside the chloroplast: it is located in special vacuoles in the cytoplasm near the pyrenoid. Mannitol performs a reserve, as well as an osmoregulatory function; its concentration inside the cell depends on changes in water salinity.

Young cells of brown algae contain small and numerous vacuoles, which become larger with age due to fusion. In the cytoplasm there are special formations - physodes, which contain phlorotannins. These substances are known only in species of brown algae. The function of phlorotannins may be associated with the protection of algal thalli from being eaten by animals, such as mollusks. Phlorotannins of brown algae probably inhibit the settlement of epiphytic algae and animals on the surface of the thallus. It is assumed that phlorotannins are involved in protection against radiation damage and in the selective absorption of heavy metal ions from the aqueous medium. Colorless phlorotannins are oxidized in air to form the pigment phycofein, which gives dried brown algae their characteristic dark color.

The structure of the thallus. Among the species of brown algae, there are no unicellular and colonial forms, all individuals are multicellular. The form of thalli of brown algae is the most diverse. These are threads, creeping or vertically standing, single-row or multi-row; massive solid or tiled crusts and crusts; thin mucous plates or dense leathery plates on the stem, simple or dissected; bubbles and bags; tubes and cords; variously branched thin bushes or powerful bushes. Attachment of thalli is carried out with the help of rhizoids or soles. To keep them in a vertical position, large benthic forms of brown algae form air (swimming) bubbles filled with gas (Fig. 29).

Rice. 29. Appearance of brown algae: 1 - Fucus; 2 - Saccharin; 3 - Alaria; 4 - Sargassum

The thalli of representatives of the orders Laminaria and Fucus are the most complex among the brown algae species. They have signs of tissue differentiation with specialization of thallus cells (Fig. 30). In their thalli one can distinguish bark consisting of intensely stained cells and core, consisting of colorless cells, which are often collected in filaments. In Laminaria, sieve tubes and tubular filaments are also formed in the core. The core performs not only a transport function, but also a mechanical one, since it contains threads with thick longitudinal walls. Between the bark and the core of many brown algae, there may be an intermediate layer of large colorless cells.

Growth thallus in representatives of brown algae is most often intercalary (intercalary) and apical (apical), rarely basal. Intercalary growth may be diffuse, or there may be a zone of growth. In large forms, the intercalary (intercalary) meristem, or an actively dividing group of cells, is located at the point of transition of the "petiole" into the "leaf" blade. Large algae also have a meristematic zone on the surface of the thallus, the so-called meristoderm (a kind of analogue of the cambium of higher plants).

reproduction in brown algae, vegetative, asexual and sexual. Gametes are formed in multi-celled gametangia, zoospores - in

Rice. 30. Internal structure Laminaria(according to: L.L. Velikanov et al., 1991): BUT- longitudinal section of the stem; B- cross section of the stem; AT- slice of a plate with sori of zoosporangia

unilocular sporangia.

Vegetative propagation in a number of species of brown algae can be carried out by thallus sites; in species kind Sphacelaria- brood twigs (brood buds); in species of the genus Fucus- a group of cells on the sole that are capable of differentiating into a new thallus.

Asexual reproduction of brown algae usually occurs with the help of zoospores. Some species reproduce by immobile tetraspores or monospores. Spores of asexual reproduction are formed as a result of meiosis and subsequent mitoses in unilocular sporangia. The sexual process is isogamy, heterogamy and oogamy. Gametes are formed in polyhedralthese gametangia- special groups of cells. One gamete is formed in each "nest" of the gametangium.

For brown algae, sex pheromones- soluble substances that coordinate the activity of cells during reproduction. Pheromones, of which at least ten are known, can either stimulate the opening of antheridia or attract male gametes to female ones. They are also involved in species isolation. It is believed that pheromones are formed in most species of brown algae that have a sexual process.

Life cycle. Brown algae have two main types of life cycles. One type is haplodiplobiont. Sporophytes are diploid, i.e. All cells contain a complete set of chromosomes. Spores of asexual reproduction are formed in unilocular sporangia. During the formation of spores, a reduction division occurs - meiosis. Such a reduction is called sporic. The cells (spores) formed after meiosis are haploid; contain half the number of chromosomes. Haploid zoospores and tetraspores germinate into a haploid gametophyte, on which gametes are formed in multi-celled gametangia. The diploid zygote formed after the fusion of gametes grows into a diploid sporophyte.

Another type is diplobiont; sporophytes, spores and gametophytes are diploid; reduction division occurs during the formation of gametes. Such a reduction is called gametic. After the fusion of haploid gametes, a diploid zygote is formed and germinates into a diploid sporophyte. This type is common in kelp species (Fig. 31).

Rice. 31. Life cycle Saccharines(according to: L.L. Velikanov et al., 1991): 1 – sporophyte, 2 – sori of zoosporangia, 3 – zoospores , 4 - gametophyte, 5 - antheridium, 6 - oogonium, 7 - antherozoid, 8 - zygote (fertilized egg)

On a macroscopic sporophyte Saccharines, at the top of the plate, stripes develop sori(groups) of zoosporangia. In zoosporangia, after reduction division, zoospores with two unequal flagella are formed. They grow into microscopic gametophytes: male with antheridia and female with oogonia. The egg fertilized by antherozoids immediately, without a dormant period, germinates and forms a sporophyte. On this life cycle Saccharines ends.

Fucus algae do not have sporophytes. At Fukusa male and female genital organs - antheridia with spermatozoa and conceptacles with oogonia and eggs - are located in the recesses of the thallus - scaphids, male and female scaphidia can be on the same receptacle or in different recipes. Oogonia sit on a cage-leg , appearing on the wall conceptcula(Fig. 32, C, D). The oogonium cell undergoes three divisions

Rice. 32. Reproduction Fukusa(according to: B. Fott, 1971; W. Braune et al., 1974): A – fragment of thallus (1 – air bubble, 2 - recipe); B– incision through the receptacles; AT– section of a female scaphidia; G- oogony; D- the release of eggs; E– section of a male scaphid; AND– branch with antheridia; 3 – sperm output

nuclei, the first of which is reduction, as a result of which 8 eggs are formed in the oogonium.

Antheridia usually form on branched filaments that support them - paraphyses(Fig. 32, E,AND). As a result of several divisions, 64 spermatozoa are formed. spermatozoa Fukusa have an eye located inside a reduced chloroplast. At the anterior end of the sperm cell, 13 microtubules form hobocurrent- a special structure, which is supposed to take part in the definition of the female sexual attractant.

Spermatozoa are attracted to the egg Fukusa fucoserraten, a nonspecific pheromone secreted by the egg. Recognition at the species level is associated with specific oligosaccharides on the egg and sperm. On the surface of the egg there are various areas, each of which contains special organic compounds - glycoproteins. Spermatozoa contain glycoproteins organized into sites on the membrane and outgrowths of the anterior flagellum, as well as on the surface of the spermatozoon itself. When meeting with the egg, the sperm moves over the shell of the egg, as if examining it with the help of its anterior flagellum. If the glycoproteins of the spermatozoon are complementary to the glycoproteins of the ovum, then only the recognition of the spermatozoon by the ovum occurs.

Systematics

Fossil finds that may be related to brown algae are known from the Middle Silurian (about 425 Ma). But these finds are also similar to some modern green and red algae. Fossil finds that can definitely be associated with modern brown algae date back to the Miocene (5–25 million years). These algae reminiscent of modern Dictiota. The age of brown algae determined by molecular methods is 155–200 million years.

The type of organization of the thallus, the presence or absence of a pyrenoid, the mode of growth, the type of sexual reproduction (isogamy, heterogamy, oogamy) and the life cycle are used to distinguish the orders of brown algae. In recent years, the system of brown algae has been actively revised. In different classification schemes, as part of the Class Brown algae, from 7 to 14 orders are distinguished.

Desmarestian order–Desmarestiales. The algae are bushy, multiply branched, with a terete, flat or flattened thallus. Attaches to the substrate with a well-developed sole. Hairs develop on the surface of the thallus.

Genus Desmarestia (Fig. 33). Brown or olive bushes with a well-defined main shoot, up to 0.8–1 m in height. Attached with a cone-shaped sole. Branching 3-4 orders, alternate or opposite. The branches of the last orders are flat or, more rarely, filiform. The species are marine, living in the arctic and temperate latitudes at a depth of 1–20 m, forming thickets or growing singly.

Rice. 33. Desmarestia (r. Desmarestia)

Ralphsian order–Ralfsiales. Representatives of the order have a thallus in the form of crusts of various structures or consist of a basal crust and vertical shoots.

Genus Analipus. The thallus consists of a perennial crust-like basal part and annual, olive-brown, vertical shoots up to 40 cm high extending from it. Multi-celled sporangia are cylindrical in shape and two-row in structure. Unilocular sporangia are oval and develop among the assimilation branches. Species of the genus are widespread in the seas of temperate latitudes, forming belts in the tidal zone.

Order Dictyota–Dictyotales.For species of the order, apical growth is characteristic. Vegetative cells contain numerous disc-shaped chloroplasts without pyrenoids. Parenchymal thallus, isomorphic alternation of generations is characteristic. The sexual process is oogamous, asexual reproduction by immobile spores, spermatozoa have only one flagellum. The flagellum is long, with pinnate outgrowths and directed forward. Representatives of the order are found mainly in tropical and, less often, in temperate seas.

Genus Dictyota (Appendix, 4A). It has a thallus in the form of flat olive-brown dichotomously branched bushes up to 11–15 cm high. The branches are linear, narrow, without veins, with forked tops. Tetrasporangia form sori on the surface of the thallus, which have an indefinite or annular shape. Distributed in sea waters of temperate and warm latitudes.

Order Laminaria–Laminariales. Laminaria have a thallus consisting of a plate, stem and attachment organs - the sole or rhizoids. The plate is even or wrinkled, entire or dissected, with holes, folds, boules or without them, from several tens of centimeters to 20–40 m long. The stem is branched or more often unbranched. Sporophytes are annual or perennial, some species are 11–18 years old. Mucous canals are located in the bark of many kelp.

The most popular representatives of brown algae are kelp (types of genera Laminaria or Saccharina), or "seaweed", which are distributed mainly in the Pacific Ocean. They are found from the surface (edge) of water to a depth of 200 m. Laminaria grow preferably at a depth of 2–20 (30) m, in places with constant movement of water, attaching to stones and rocks. Laminaria form algal belts along the coast of the seas of the Far East. The most powerful thickets are found near the Kuril Islands and at about. Hokkaido, where about half of the world's laminaria resources are concentrated. The annual world harvest of kelp algae reaches 2 million tons of fresh weight, while more than 1 million tons comes from the production of its mariculture in China.

Genus Saccharin (Laminaria). The thallus is from 0.5 to 5–10 m long, has a thick shiny plate, an elastic stem and densely intertwined rhizoids, which are attached to various solid substrates. The edges of the plate are smooth or wavy; there are often bulges and folds on the surface of the plate. Accumulations of sporangia - sori - are formed on both sides of the plate, after the release of spores, the upper part of the plate is destroyed. Lives from two to several years. Saccharins are a valuable industrial raw material and an object of mariculture. Saccharina Japanese forms thickets in the northern half of the Sea of ​​Japan, as well as near the southern and southeastern coast of Sakhalin and the South Kuril Islands. Saccharina Japanese is the most valuable commercial species, it has excellent taste and is used to prepare a variety of dishes, canned food, confectionery.

Order Sphacelariae–Sphacelariales.

Brown algae belonging to this order have a branching thallus with apical growth. Hairy branches. Vegetative cells have numerous chloroplasts without pyrenoids. The life cycle of the majority with an isomorphic change of generations, the sexual process is isogamy or heterogamy. Algae form small brown bunches up to 3 cm in height and branched bushes up to 20 cm in height on stones or other algae; there are endophytic representatives.

Genus Sphacelaria. It has thin thallus. Branching filaments form small, up to 0.5–3 cm in height, brown tufts. Vegetative reproduction is carried out by specialized, often three-beam brood branches - propagules. The sexual process is isogamous. The female gametes secrete the pheromones ectocarpen and multifiden. Species of the genus are distributed in the seas of both polar and tropical latitudes.

Order Scytosiphon–Scytosiphonales. Representatives with intestinal, vesicular, lamellar or saccular, often hollow thallus up to 25 cm in length. The bark is single-row or two-row, the inner part (wall) of the thallus is formed by several layers of large cells. On the surface of the thallus, multi-celled sporangia develop, which are collected in sori that support their threads - paraphyses and tufts of hairs.

Genus Scytosiphon is a thin-walled brown tube 4–25 cm long (Appendix 4B). The thallus is attached with a small sole and has rare transverse constrictions. It occurs in the coastal zone of the seas at various latitudes, often forms belts in the tidal zone.

Fucus order–Fucales. They have a perennial thallus in the form of large irregularly or dichotomously branching bushes up to 1–3 m in length. They are attached to the substrate with a cone-shaped sole. Thallus have shoots, phylloids (leaf-like formations), receptacles (receptacles of gametes) and swimming (air) bladders. They are found in the tidal zone of all temperate and arctic seas, where they form powerful thickets - belts.

Genus sargassum(Fig. 34, AT). Abundantly branched olive-brown or brown bushes 0.5–1.5 m high. Attached with a conical sole. Phylloids develop on lateral shoots extending from the cylindrical stem in the lower and middle parts of the thallus. Phylloids are leathery, with a central rib, 0.2–2 cm long. Swim bladders are oval or rounded, with or without outgrowths. Sargassums are widespread in temperate and subtropical latitudes from the lower littoral to a depth of 10 m, where they form dense or sparse thickets. In the South Pacific Ocean - the so-called Sargasso Sea - they form vast floating accumulations in which they reproduce only vegetatively.

Genus Fucus (Fig. 32).Thallus leathery, bushy, branches dichotomously, 25–50 cm high. Near the coast of the Far Eastern seas, it grows for several years, lives in the littoral zone. Often forms large thickets in shallow water. Species of this genus are characterized by dichotomous

Rice. 34. The appearance of fucus algae: BUT – Ascophyllum; B – Cystoseira; AT – sargassum; 1 - receptacle, 2 - swim bladder

a branched thallus with flat branches having a longitudinal rib, which is attached to the stones with a conical sole. Fucuses are used as fertilizers, as feed for livestock, for the production of feed flour, alginates, used in medicine for the treatment of goiter, weight correction, etc.

Order Ectocarps–Ectocarpales. The algae that are included here are microscopic, free-living, epiphytes, epizoites, or endophytes. Reproductive organs are represented by unilocular (sporangia) and multilocular (gametangia) sporangia; they are long-cylindrical, short-cylindrical or pod-shaped.

Genus ectocarpus. Thallus in the form of soft brown bushes up to 2 cm in height. The bushes are formed by single-row, alternately, dichotomously or incorrectly branched threads. Multi-celled sporangia are pod-like, formed on the side of lateral branches on a 1–3-celled stalk. The species are distributed in the seas of different latitudes, in clean and polluted waters, in the littoral and in the upper part of the sublittoral. Epiphytes are also found in the fouling of anthropogenic substrates.

Ecology

The vast majority of brown algae live in marine waters. Only 8 species are found in fresh waters. There are both annual and perennial species, the age of which can reach 15–18 years. Laminaria algae Nereocystis and Macrocystis, which live along the Pacific coast of North America, have the maximum size for all algae - up to 30–40 m in length. They form giant underwater forests in the seas of the Far East. Brown algae attach to a wide variety of substrates - rocks, stones, gravel, shells and shells of marine animals, and other algae. Some small forms of brown algae live inside the tissues of other algae as endophytes. Most brown species live in an attached state. The thallus torn off from the ground are carried by the current to calm places with a muddy bottom and continue to exist there. Species with air bubbles on the thallus, breaking away from the ground, float to the surface, forming large floating clusters, especially in areas with a stable circular current, as in the Sargasso Sea. They exist in such clusters for quite a long time and reproduce only vegetatively.

Brown algae are widespread in all seas, but they reach their greatest development in the seas of temperate and subpolar latitudes. Their large thalli grow attached to rocks and stones, and in quiet places near the coast and at great depths they can even be held on the valves of mollusk shells and gravel. You can meet them at different depths - from the littoral zone, where at low tide they are out of water for hours, up to 40–200 m. In the area of ​​the Hawaiian Islands, at a depth of 180 m, species of the genus sargassum, a Kelp in The Adriatic Sea was found at a depth of 200 m. The most abundant thickets of brown algae are observed at a depth of 6–15 m, where the best lighting conditions and the constant movement of water, which brings nutrients to their thalli and limits the settlement of herbivorous animals - phytophages.

Class Golden algae -Chrysophyceae

Unicellular, colonial, or multicellular organisms, usually having a flagellar stage in their life cycle. Cells are mononuclear, with one or more chloroplasts. Stigma is usually present (Fig. 36). Flagella 1–2, unequal. The contractile vacuole is located in the anterior part of the cell. The outer covers of the cells of these organisms are very diverse. In the most primitive species, the cell is dressed in a delicate periplast, which allows the formation of protrusions of various shapes (rhizopodia, pseudopodia), in others, the plasmalemma is covered with a hard cellulose membrane, sometimes strongly mucilaginous. Houses in golden algae come in different shapes: vase-shaped, spherical, ovoid, cylindrical; with one or more holes. The cage is attached to the base of the house with a flexible leg or can be free. In some chrysophytes, calcareous formations - coccoliths - of various shapes and sizes are deposited on the cell surface, and silicon flagellates have an internal silicon skeleton. The diversity of the structure of these skeletons makes it possible to use the remains of various forms of fossil silicoflagellates to determine the age of the geological rocks containing them. In more highly developed representatives of the department of golden algae, the cells are dressed in a shell consisting of silicon scales (sometimes bearing spikes), or enclosed in houses, through the holes of which flagella or pseudopodia come out.

Houses in species of golden algae are vase-shaped, spherical, ovoid, cylindrical, with one or more holes. The cage is attached to the base of the house with a flexible leg or can be free.

Pigments - chlorophylls a and With, fucoxanthin. Chrysophytes are characterized by the highest content of fucoxanthin among heterokonts (55-93% of all carotenoids).

Most species are freshwater phototrophs, but heterotrophs and phagotrophs are also found.

Spare substances - chrysolaminarin and oils.

Among unicellular forms of golden algae, freshwater planktonic species predominate, and among multicellular forms, benthic or epiphytic ones. They are found mainly in cool sea and fresh water bodies. About 360 species are known.

Rice. 36. Golden algae (according to: C. Hoek van den et al., 1995): BUT- cell structure; B- radicular system; AT- tripartite mastigonema; G- section of a part of the chloroplast; 1 - basal body; 2 - basal swelling; 3 - short flagellum; 4 - stigma; 5 - rhizoplast; 6 - core; 7 - nuclear membrane; 8 - nucleolus; 9 - mitochondrion; 10 - vacuoles; 11 - mucus; 12 - plasmalemma; 13 - vesicles; 14 - mucous body; 15 - lipids; 16 - chloroplast; 17 - Golgi apparatus; 18 - contractile vacuole; 19 - long flagellum: 20 - 1st root; 21 - 2nd spine; 22 - 3rd spine; 23 - 4th spine; 24 - chloroplast nucleoid; 25 - HES; 26 - chloroplast shell; 27 - girdle lamella; 28 - lamella; 29 - long lateral filament; 30 - short lateral filament; 31 - terminal filament; 32 - tubular part of mastigonema

thallus structure in golden algae, it is most often monadic, but can be very diverse: coccoid, palmelloid, plasmoidal, amoeboid, filamentous, parenchymal (Fig. 37).

Rice. 37. Golden algae (according to: L.L. Velikanov et al., 1981): BUT – Ochromonas: 1 - appearance, 2 - cyst; B – Chromulina: 1 - appearance, 2 - cyst, 3 - scheme of formation of a film from cysts; AT – Dinobrion: 1 - general view of the colony, 2 - cyst; G – Chrysameba; D – gibberdia; E – Hydrurus: 1 - general view of the colony, 2 - branch tip, 3 - zoospore

reproduction. In golden algae, there are three methods of reproduction: vegetative, asexual and sexual.

Vegetative reproduction occurs by longitudinal cell division or the breakdown of a colony into parts due to cell division in one, two or three directions.

sexual process(cells of golden algae are diploid) - isogamy or conjugation. As a result of the sexual process, as well as under adverse conditions, cysts are formed with a thick shell containing silicon.

asexual reproduction carried out by one- or two-flagellated zoospores, which develop in ordinary vegetative cells or zoosporangia. Sexual process: holo-, iso- and autogamy. Hologamy is a type of sexual process in which two cells similar to vegetative cells merge at the anterior ends into a binuclear zygote, which then turns into a silicified cyst.

Systematics

From Golden algae at the end of the last century, based on the results of molecular genetic studies, the Sinuraceae class was isolated. The class Feotamniaceae is also distinguished - from Yellow-green and Golden algae. Therefore, the scope of the class Chrysophyceae has been reduced and currently includes about 360 species assigned to three orders: Chromulinales, Hibberdiales and Hydrurales. The shape, structure, and number of flagella, as well as the pigment composition and structure of the body, are important systematic features.

Chromulin order - Chromulinales. This order includes organisms with monadic, palmelloid and amoeboid types of thallus differentiation. Monadic cells with one flagellum visible under a light microscope.

Genus Chrysameba(Fig. 37, BUT) - freshwater amoeboid algae, they have a flagellar stage in their life cycle. The zygote develops into a stomatocyst.

Genus Chromulina(Fig. 37, AT) - unicellular free-swimming organisms that live mainly in fresh waters. Cells are naked; there are one or two golden plastids.

Genus Dinobrion(Fig. 37 , G)- unicellular and colonial, free-floating or attached representatives. Monads are located in vase-shaped houses formed by cellulose microfibrils. In addition to cellulose, the house also contains a large number of amino acids. The bushy form of the colonies is associated with the method of vegetative cell division, when one of the daughter cells, leaving the parental house, attaches to its hole. Rotating around its axis, it forms its own house. Both child cells can also leave the parent house. The cells contain 1-2 chloroplasts; an eye and 2 contractile vacuoles are visible at the anterior end of the cell. Chrysolaminarin is located in a vacuole at the posterior end of the cell. Reproduction is vegetative and sexual.

Order Gibberdiae–Hibberdiales. Representatives of this order are characterized by a unique pigment composition. In addition to fucoxanthin, they have an additional light-harvesting carotenoid pigment, antheraxanthin.

Includes childbirth Gibberdia, Chromophyton, Styloceras, Chrysopixis, Platyteka and others.

Genus gibberdia has two stages in the life cycle: colonial palmelloid immobile and unicellular monadic motile. With light microscopy, only one flagellum is visible in the monadic stage. In addition to fucoxanthin, the presence of another additional light-harvesting carotenoid pigment, antheraxanthin, is characteristic.

Order Hydrorus–Hydrurales. Representatives of this order have a thallus with palmelloid and pseudoparenchymal types of structure. The presence of unique tetrahedral zoospores is characteristic. There is no eye. Mitosis is semi-closed.

Includes childbirth Hydrorus, Celloniella, Federmatium, Chrysonebula and others.

Genus Hydrurus(Fig. 37, E) is the most differentiated among palmelloid algae. Its thallus is large, up to 30 cm long, slimy colonies that look like brown branched cords, often emitting a very unpleasant odor. In colonies, one can distinguish between the main trunk and lateral branches. Cells immersed in common mucus contain one cup-shaped chromatophore and several contractile vacuoles. The cells are loosely located along the periphery of the colony and denser in the middle. The thallus can only grow by dividing apical cells. During asexual reproduction, zoospores are formed in the cells of the lateral branches of the colony. Forms spherical cysts. It occurs in mountain streams and rivers with cold water, where it attaches to hard substrates.

Class Sinura algae -Sinurophyceae

syn- together and ura- tail. This group of organisms was isolated in 1987 from golden algae. It unites monadic single and colonial organisms, sometimes with alternation in the life cycle of the monadic and palmelloid stages. The surface of the pectin shells is covered with a shell of silicon flakes. Mitochondria with tubular cristae are usually located in the cytoplasm around the chloroplast. The nucleus is one, chloroplasts surrounded by four membranes, usually two. The lamellae are trithylakoid, there is a girdle lamella. The main pigments are chlorophylls a and With, β -carotene and fucoxanthin. There is no stigma. Cells usually with 2 unequal flagella. The long pinnate flagellum is directed forward. Short, smooth flagellum, sometimes strongly reduced, directed posteriorly.

Cells reproduce mainly by longitudinal division. Colonies, breaking up, give rise to young colonies. In some species, the sexual process is described in the form of isogamy. At the same time, unlike golden algae, the fusion of isogametes in sinuric algae occurs not at the anterior, but at their posterior ends. Silicified cysts with pores are formed endogenously, similar to those of chrysophytes.

Predominantly planktonic forms, palmelloid stages are part of the benthos. Most species of sinura algae are phototrophic freshwater organisms.

Systematics.

The class Sinura algae includes 7 orders: Chloramoebales, Synurales, Rhizochloridales, Ochromonadales, Heterogloeales, Parmales and Thallochrysidales.

Order Sinura - Synurales. Monadic forms, pectin cell membranes are usually covered with a shell of silica flakes, cemented with organic matter into a single case. Chloroplasts one or two.

Genus Sinura(Fig. 38) - freshwater monadic forms with two unequal flagella and two parietal chloroplasts. The nucleus is pear-shaped, located in the anterior part of the cell. Behind the nucleus there is one large vacuole, and in the back of the cell there are several small contractile vacuoles. The cells are covered with scales, like tiles. Reproduction is most often vegetative, for some the sexual process is known. Forms colonies (Fig. 39, A). Often, cysts appear in all cells of the colony. With mass development Sinura may give the water an unpleasant odor.

Rice. 38. Appearance of Sinura cells

Order Rhizochloride - Rhizochloridales. Predominantly freshwater organisms with a rhizopodial type of thallus differentiation, living mainly in fresh water bodies.

Genus Mallomonas(Fig. 39, B-D) – unicellular monad with one well-marked flagellum and one bifurcated chloroplast.

Rice. 39. Appearance of sinuric algae (according to: G.A. Belyakova et al., 2006): BUT – fissile colony Sinura; B, C – statospore formation and G – appearance Mallomonas

The cell is covered with tiled and spiral scales, some of them bear needle-like spines (Fig. 39, G). The presence of statospores is characteristic (Fig. 39, B, C). For a number of representatives, the sexual process, hologamy, is described.

Genus Mixochloris lives in the cells of the leaves of sphagnum mosses, has the appearance of a large multinucleated plasmodium. It forms cysts in autumn, which germinate in spring. Zoospores or amoeba emerge from them, penetrating into empty leaf cells and merging there into plasmodium.

Order Chloramoebaceae - Chloramoebales. Includes monad representatives. Found in salt and fresh waters.

Genus heterochloris – its cells can change shape, forming pseudopodia. This phenomenon is inherent in many representatives of the order, as well as the tendency to the animal mode of nutrition. There are several chloroplasts, oil drops and chrysolaminarin in the cell. In front of the cell there are contractile vacuoles, in the center - one nucleus. Reproduces vegetatively by cell division.

Order Ochromonadales - Ochromonadales. Combines bare forms with two unequal flagella. Freshwater and marine forms.

Genus Ochromonas includes unicellular monads with two unequal flagella. Cells are dressed only by plasmalemma. At the anterior end of the cell there is a contractile vacuole and an eye, at the posterior end there is a vacuole with chrysolaminarin. It reproduces vegetatively, the fission furrow begins at the anterior end of the cell between two pairs of flagellar bases. Species of the genus are common in oligotrophic fresh waters, but there are also marine representatives.

Order Heterogleyes - Heterogloeales. Includes algae with palmelloid type of thallus differentiation. Representatives of the order are found more often in fresh than in salt waters.

Genus Helmintoglea lives in brackish waters. This colony, sitting on an expanded base, consists of branching slimy bands. Protoplasts are randomly arranged in this mucus, each of which is surrounded by its own mucous wrapper.

Phaeotamnia algae class - Phaeothamniophyceae

The name of the class comes from the type genus Phaeothamnion(from Greek. phaeos- swarthy bush). Representatives of this group of organisms were identified in a separate class from yellow-green and golden algae in 1998 based on the analysis of the sequence of ribosomal genes and features of the cell ultrastructure. Feotamnia algae are characterized by a unique combination of pigments: fucoxanthin with heteroxanthine, the absence of violaxanthin.

Features of the cell structure: the absence of vacuoles with chrysolaminarin and the absence of endogenous cysts with silica walls.

The class includes unicellular, colonial and multicellular organisms with coccoid, palmelloid and filamentous type of thallus structure. Flagellated stages with two unequal flagella. Flagella lateral or subapical. Stigma is found in zoospores. Pigments - chlorophylls a and With, β -carotene, fucoxanthin, diadinoxanthin, diatoxanthin and heteroxanthin. The main spare product is paramylon ( β -glucan). The cell wall is present, during cell division the daughter wall is formed inside the parent wall.

In the feotamniaceae, of the main methods of reproduction, only vegetative and asexual are found. Asexual reproduction is carried out by autospores or zoospores. Sexual reproduction is unknown.

Species of Feotamnia algae live exclusively in fresh waters. Systematics.

At present, the monophyletic class of pheotamnia algae has been confirmed, and among ochrophytes it is closer to brown and yellow-green algae than to golden algae. Currently, about 30 species of these algae are known, attributed to one order Theotamnia - Phaeothamniales.

Genus Theotamnion represents attached branching threads up to 1 cm in height (Fig. 40). Cells are cylindrical, irregular, expanded upwards, along

Rice. 40. Appearance Theotamnion.

two to three times longer than wide. During cell division, the material of the parental wall is consumed for the formation of a layered sheath surrounding the filament cells. On the periphery of the cell under the plasma membrane there are vesicles. They resemble physodes - formations found in the cells of brown algae. Cells contain from one to several disk-shaped olive-brown plastids. Zoospores are formed by 1–2, less often by 4–8 in one cell. In zoospores, flagella are attached laterally. The position of the flagellar roots Theotamnion resembles that of yellow-green and brown algae. It also lacks a rhizoplast. In the life cycle, cysts can form, but there is no silicon in their walls. Cysts germinate as zoospores. Settles as an epiphyte on filamentous algae. Inhabits stagnant and slowly flowing fresh water bodies.

Class Rafid algae -Raphidophyceae

The name of the class comes from the Greek rhaphid - needle. Unites unicellular biflagellate organisms devoid of a cell wall. Mostly freshwater organisms with flattened cells (Fig. 41).

The cells have flagella of unequal length; the flagellum directed forward is pinnate and longer; the flagellum directed backward is smooth and shorter. The transitional spiral is missing. Chloroplasts are small, numerous or, more rarely, 1-2 per cell, surrounded by four membranes, of which two are CES membranes. The thylakoids are arranged in stacks of three. The nucleus is large, surrounded by a ring of dictyosomes. Mitochondria with tubular cristae. There are contractile vacuoles. The cytoplasm is often vacuolated. The cells are naked, surrounded only by the plasmalemma. Stigma (eye) is usually absent.

Photosynthetic pigments - chlorophylls a and With, β -carotene, vosheriaxanthin, dinoxanthin, diadinoxanthin, heteroxanthin.

Spare assimilation products are fats and oils, less often starch and chrysolaminarin.

They also live in sphagnum bogs and other habitats with acidic and neutral water reactions. Some species are found in brackish and marine waters.

Rice. 41. Appearance of raphid algae.

Systematics.

For a very long time, this group of algae, due to its green color, the presence of a pharynx, and a number of other structural features, was considered as a class of Chloromonas among Euglenoids. But the data of cytology, biochemistry, physiology and molecular biology showed their undoubted belonging to the Heterocont (Ochrophyte) algae division and the monophyletic nature of the Rafid algae group.

About 25 species are known from the only order Huttonellaceae– Chattonellales.

Genus heterosigma(Fig. 42, BUT) includes marine flagellates. Oval-shaped cells with flagella shifted to the side, plastids are located along the periphery of the cell. There are no trichocysts. They swim, making rotational movements around the longitudinal axis of the body. May cause toxic "water blooms" in coastal waters.

Rice. 42. Rafid algae (by: R. E. Lee, 1999): BUT – heterosigma; B – Goniostomum; 1 - chloroplast; 2 - mucocyst; 3 - contractile vacuole; 4 - trichocyst; 5 - core

Genus Goniostomum(Fig. 42, B) are mobile dorsoventrally compressed monads. The dorsal side is curved, the ventral side is flattened. A furrow at the anterior end leads into a triangular pharynx, from which two long flagella emerge; their length is comparable to the length of the cell. Plastids are located at the periphery of the cell. Beneath the plasmalemma are trichocysts. Lives in fresh waters with an acidic pH.

Class Eustigma algae -Eustigmatophyceae

The name of the class comes from the Greek eu- "good" and stigma- "mark", "spot". The class unites naked unicellular, less often colonial, organisms of predominantly coccoid structure.

One or more cores. The chloroplast is usually one, surrounded by 4 membranes. The flagellum is usually one anterior pinnate and a second basal body or, more rarely, two unequal flagella. Stigma (eye) is present, located outside the chloroplast, its granules without membranes.

Rice. 43. Appearance of Eustigma algae

The chloroplast is usually single, large, multi-lobed, cup-shaped or parietal, yellow-green in color. Thylakoids are grouped into lamellae in groups of three; the encircling lamella is absent.

The main pigments are chlorophyll a, β-carotene, violaxanthin and vosheriaxanthin. The pyrenoid is usually present only in vegetative forms.

Spare substances are oils and a substance of an unknown nature, which is deposited as a solid material outside the plastids. Starch is not formed.

They live in fresh waters, are less common in the seas and in the soil.

Systematics.

Previously, this group of organisms was classified as yellow-green algae. Currently, Eustigma algae are considered at the rank of a class in the department of Heterocontophytes. About 35 species are known, mostly freshwater, attributed to the only Eustigma order - Eustigmatales.

Genus Eustigmatos(Fig. 43) - unicellular small spherical algae. The cell wall is smooth, entire, without ornamentation. Yellow-green chloroplast single, lobed, parietal, with stalked polyhedral pyrenoids. Large central vacuole with red contents. It reproduces by 2 or 4 autospores or bottle-shaped zoospores with one incoming flagellum, a large stigma located outside the chloroplast at the anterior end, and a single posterior chloroplast without a pyrenoid. A common component of soil flora. Known from New Zealand, Austria, Iceland, and from the Arizona basins as "mustard seaweed".

Class Yellow-green algae -Xanthophyceae

Yellow-green algae are those whose chloroplasts are colored light or dark yellow, very rarely green, and only sometimes blue. The color of thalli is determined by the presence of the following pigments in the chloroplast cells - chlorophylls a and With, β -carotene and xanthophylls. The predominance of the latter determines the originality of the color of yellow-green algae. In addition, paramylon, oil drops, and only in some species, in addition, lumps of leukosin and volutin accumulate in the cells as the main product of assimilation. Yellow-green algae do not form starch. A distinctive feature of yellow-green is the presence of a monadic structure in vegetative cells and two unequal flagella in zoospores. The cell wall contains cellulose, glucose and uronic acids. The cell wall often consists of two parts.

Reproduction is vegetative, asexual and sexual.

Widely distributed in fresh waters. Rarely found in marine, brackish waters and in soil.

Previously, the yellow-green algae class was called Tribophytium algae, after the type genus Tribonema (from the Greek. tribon – skillful, cunning and nema – a thread). About 450 species are known.

Yellow greens are characterized by significant morphological diversity. Among the numerous representatives of this department, almost all the main types of body structure are found: amoeboid, monadic, palmelloid, coccoid, filamentous, multifilamentous, lamellar and siphonal (Fig. 44 – 46). Thallus unicellular,

Rice. 44. Appearance of yellow-green algae: 1, 2 - Charatiopsis, 3 – Centritractus, 4 – ophiocytium

colonial, multicellular and non-cellular. The cell membrane is dense, pectin and cellulose, consisting of tightly overlapping parts or of two valves. Silica or lime is deposited in the shell. Mostly fixed forms. Among unicellular species, there are mobile forms, devoid of a dense shell and equipped with flagella, lobopodia and rhizopodia.

Rice. 45. Appearance of xanthococcal yellow-green algae: 1–3 - Botrydiopsis, 4 – tetrahedriella, 5 – Pseudostaurastrum, 6 – Goniochloris, 7, 8 – Bumilleriopsis

Most yellow-green – immobile organisms. In mobile individuals, movement can be carried out using flagella or rhizopodia. Cells of various shapes: spherical, spindle-shaped, ellipsoid, cylindrical, tetrahedral, sickle-shaped, pear-shaped, ovoid. Thallus sizes from 0.5 – 1.5 µm ( Chloridella) up to several millimeters in diameter ( Botrydiopsis) (Fig. 45, 1 – 3) and up to tens of centimeters in length ( Vosheria) (Fig. 46, 3).

Rice. 46. ​​Appearance of yellow-green algae: 1 - Tribonema, 2 – heteropedia, 3 – Vosheria, part of a filament with oogonium and antheridium

Most yellow-green species are phototrophs, but holozoic feeding by ingestion of bacteria and small algae is also found. Yellow-green algae are widely distributed in fresh waters. They are also common in soil, less common in marine and brackish waters. The class includes aerobiont, planktonic, benthic and periphytonic forms. Epiphytes, epizoites, as well as intracellular symbionts in protozoan cells.

Regardless of the external structure, the internal structure of the cell of yellow-green algae is the same. In the protoplast, there are usually several yellow-green chloroplasts that have a disc-shaped, trough-shaped, lamellar, less often ribbon-shaped, stellate or cup-shaped shape with entire or lobed edges. The coloration is due to the absence of fucoxanthin, which is responsible for the golden and brown color in other ochrophytes. Of the other pigments they have β -carotene, vosheriaxanthin, diatoxanthin, diadinoxanthin, heteroxanthin. In mobile forms, a red eye, or stigma, is usually located at the anterior end of the chloroplast. Few species have pyrenoids of a semi-submerged type. The nucleus in the cell is usually one, small in size, but there are species with multinucleated cells. Some species have one or two contractile (pulsating) vacuoles in the anterior part of the cell.

The monad representatives and the motile stages (zoospores and gametes) have two unequal flagella. The exception is synzoospores. Vosheri, in which numerous pairs of smooth flagella slightly different in length are located along the surface. A short flagellum ends with an acroneme. The flagella are attached to the cell subapically. At the spermatozoon Vosheri lateral attachment.

In species with an amoeboid, monadal, and palmelloid organization, the cell wall is absent, they are covered only by a cytoplasmic membrane, and can easily change shape. Sometimes "bare" cells are found inside houses, the walls of which can be painted brown with manganese and iron salts. The vast majority of forms have a cell wall consisting of two parts. Cellulose predominates in the composition of the cell wall, and also contains polysaccharides, consisting mainly of glucose and uronic acids. In young cells, the membrane is thin, with age it thickens. Iron salts can be deposited in it, the compounds of which color it in various shades of brown and red tones. More often, silica is present in the cell wall, giving it hardness and luster. It can also be encrusted with lime and be sculptured in various ways (spines, cells, warts, setae, denticles, etc.) An outgrowth of the shell can form in attached forms – foot with attachment sole.

In filamentous forms of yellow-green algae with bivalve shells, when the filaments break down, the cell membranes fall apart into H-shaped fragments. These fragments are tightly connected halves of the shells of two adjacent cells (Fig. 47). During the growth of the filaments, an H-shaped fragment of the cell wall of two neighboring daughter cells is embedded between the two halves of the membrane of the mother cell. As a result, each of the daughter cells is half covered with the old membrane of the mother cell and half – newly formed shell.

Rice. 47. Scheme of the formation of a transverse septum between two daughter cells in filamentous yellow-green algae (according to: A.A. Masyuk, 1993): BUT- a fragment of a thread; B- laying of the girdle ring and the formation of a transverse partition between two cells; AT– layering of bivalve cell membranes; G– disintegration of the shell into H-shaped sections

Contractile vacuoles are present in mobile representatives. Usually there are 1-2 per cell. Golgi apparatus of a peculiar structure. Dictyosomes are small, contain 3-7 cisterns. The nucleus is one, less often there are many; in coenotic species, cells are always multinucleated.

reproduction. Most species of yellow-green algae are characterized by vegetative and asexual reproduction.

Vegetative reproduction carried out in various ways: cell division in half, the collapse of colonies and multicellular thalli into parts. At Vosheri special brood buds are formed.

At asexual reproduction A variety of spores can form: amoeboids, zoospores, synzoospores, autospores, hemisoospores, hemiautospores, aplanospores. Zoospores are "naked" and usually pear-shaped.

sexual process- isogamy, heterogamy and oogamy - described in a few representatives. At Tribonemes gametes are similar in size, but differ in behavior - this is isogamy. At Vosheri oogamy is observed: receptacles of female gametes are formed on the threads – oogonia and male – antheridia.

Under unfavorable conditions, cyst formation is observed. Cysts (statospores) are endogenous, mononuclear, rarely multinuclear. Their wall often contains silica and consists of two unequal or, more rarely, equal parts.

Systematics.

At the end of XIX – early 20th century various genera of yellow-greens were assigned to the department of green algae, which was associated primarily with the color and morphological similarity of thalli. Yellow greens are currently considered as a class within the ochrophyte division.

About 450 modern species of the yellow-green algae class are known, which are grouped into four orders: Botridia, Mishococcus, Tribonem and Vosheria. The classification of orders is based on the type of differentiation of the thallus and the features of the life cycle.

Order Botridiae - Botrydiales. The order includes species with a siphonal type of thallus differentiation, in which there is no oogamous sexual process.

Genus Botridium lives on the soil and has the appearance of green bubbles a few millimeters in size, attached with colorless rhizoids. The thallus is siphonal, contains numerous nuclei and plastids. The shell is multi-layered, lime can be deposited on it. Reproduction is asexual with the help of biflagellate zoospores, while the entire contents of the bladder breaks up into single-nuclear fragments. With a lack of moisture, it reproduces with the help of aplanospores or forms thick-walled cysts. In some cases, the entire contents of the bladder goes to the formation of one large cyst. In other cases, cysts form in rhizoids, where the contents of the bladder first pass. The cysts germinate either directly into the new thallus or form zoospores. The sexual process is iso- and heterogamy. The zygote germinates immediately, without a dormant period. Common and widespread species in terrestrial habitats, found along the banks of streams, ponds or on soils devoid of vegetation.

Order Mischococcal–Mishococcales. Unicellular or colonial representatives with a coccoid type of thallus differentiation.

Genus Charatiopsis includes unicellular attached forms. During reproduction, it forms zoospores, aplanospores and thick-walled cysts (Fig. 44, 1-2).

Genus ophiocytium(Fig. 44, 4) has elongated cylindrical cells, which can be straight, bent or spirally twisted, and at the end can carry a spike. The cell wall consists of two unequal parts, of which the larger part is involved in cell growth, the smaller part is permanent and has the shape of a cap. Single-celled and colonial species, free-living or attached to the substrate with a small stalk. They reproduce by zoospores and aplanospores, cysts are found. They live in fresh waters.

Genus Mischococcus forms tree-like attached colonies. Branching is dichotomous and tetrachotomous. Cells are located in 2 or 4 at the tops of the mucous branches of the colony. Cells are spherical to oval, with a thin or thick cell wall. Sometimes the cell wall is shiny and brown due to its impregnation with iron salts. Young single-celled organisms with a slimy, disc-shaped base that serves as a fulcrum for attachment. After the release of the spores, the protoplast of the mother cell turns into a jelly and stretches, the length becomes 6 times greater than the width, and thus a cylindrical leg appears. The empty cell wall of the mother cell always becomes the base of the stem. Asexual reproduction by zoospores and autospores. Autospores are attached to the upper edge of the mucous stalk. Subsequent cell divisions repeat the process and produce a tree-like colony. sexual process – isogamy. They live in small fresh water bodies as epiphytes of filamentous algae. Known in Central Europe and Asia.

Order Tribonemaceae - Tribonematales. Representatives have a filamentous, multi-filamentous, false-tissue and tissue type of thallus differentiation. Cell walls are either with H-shaped overlapping parts or are solid.

Genus Tribonema- non-branching threads (Fig. 46, 1). Cells are cylindrical or barrel-shaped. The cell wall consists of two halves, which are found with edges on top of each other in the middle of the cell. Shells are often layered. Fragments of threads always end in empty halves of H-shaped shell fragments that look like a fork. There are several yellowish-green plastids in the cells, there are no pyrenoids. Reproduction is vegetative (fragmentation of filaments), asexual (by zoospores and aplanospores), and sexually (isogamy), with aplanospores being produced more frequently than zoospores. Can form akinetes. They live in fresh waters, where they develop especially abundantly in the cold season.

Order Vosherievye - Vaucheriales. All representatives have a siphonal thallus, an oogamous sexual process, and synzoospores.

Genus Vosheria(Fig. 46, 3) has a thallus of a non-cellular structure; its thallus reaches a length of several centimeters, attaches to the substrate with the help of a colorless rhizoid. There are no partitions in the threads, most of the thallus is occupied by the vacuole, and numerous nuclei and plastids are located along the periphery in the cytoplasm. Threads with apical growth and rare lateral branching. Partitions are formed when the thallus is damaged and to separate the reproductive organs. Asexual reproduction is carried out by aplanospores, synzoospores, akinetes. Synzoospores are formed one at a time in the zoosporangium, which is separated from the vegetative cells by a septum at the end of the filament. Zoospores are multinucleated and multiflagellated. The sexual process is oogamy. The zygote is covered with a thick shell and, after a dormant period, grows into a new thallus.

Kinds Vosheri widely distributed in fresh, brackish and marine waters, as well as in terrestrial habitats. They are found on all continents, including Antarctica. They form grassy-green or dark green intertwined masses - the so-called mats, smooth, creeping or cushion-shaped. Aquatic, semi-aquatic, terrestrial forms. They live in a variety of habitats: seas, estuaries, estuaries, salt marshes, mangroves, streams, canals, lakes, ponds, arable land and swamps.

Meaningheterokont algae

From the Heterocont algae department, brown algae are of the greatest importance for natural ecosystems and for humans.

Brown algae - the main source of organic matter in the coastal zone of the seas. Their biomass in the seas of the temperate and subpolar zones can reach several tens of kilograms per square meter. Thickets of brown algae provide conditions for feeding and reproduction of many coastal animals and other algae. Charles Darwin observing brown algae off the coast of South America Macrocystis, wrote: “I can only compare these vast underwater forests of the Southern Hemisphere with the terrestrial forests of tropical regions. And yet, if a forest were to be destroyed in some country, I don’t think that even approximately the same number of animal species would die as with the destruction of this algae.

Thickets of brown algae serve food place,shelter and breeding many animals. Figuratively speaking, brown algae provide other aquatic organisms with a "table, shelter and nursery."

Brown algae are widely used by humans. They are rich iodine and other micronutrients. The peoples of Southeast Asia traditionally use them for food, especially representatives of the kelp order, from which a wide variety of dishes are prepared. Feed meal, prepared from brown algae, increases the productivity of livestock; at the same time, the content of iodine increases in eggs and milk.

From brown algae receivealginates- salts of alginic acid. Alginates are widely used in various industries. These are non-toxic compounds with colloidal properties, so they are widely used in the food and pharmaceutical industries. Alginic acid and its salts are capable of 200-300-fold water absorption, forming gels, which are characterized by high acid resistance. In the food industry, they are mainly used as emulsifiers, stabilizers, gelling and water-retaining components. For example, dry powder sodium alginate is used in the production of powdered and briquetted soluble products (coffee, tea, milk powder, jelly, etc.) for their rapid dissolution. Aqueous solutions of alginates are used for freezing meat and fish products. Up to 30% of the total volume of alginates produced in the world goes to the food industry.

In the textile and pulp and paper industries, alginates are used to thicken paints and increase the strength of their bond with the base. Impregnation of fabrics with some alginates gives them protective properties: water resistance, acid resistance and increases mechanical strength. A number of salts of alginic acids are used to obtain artificial silk. During the Second World War in the USA and England, a large amount of camouflage fabric and nets for residential and industrial buildings was produced from alginic acid and its salts.

Alginates are used in metallurgy: in the foundry they improve the quality of the molding earth. Salts of alginic acid are used in the production of electrodes for electric welding, which make it possible to obtain higher quality welds. Alginates are also used in the production of plastics, synthetic fibers, coatings, and weather-resistant building materials. They are used in the manufacture of high-quality lubricants for machines. In radio electronics, alginates act as a binding agent in the manufacture of high-quality ferrites.

The greatest application is found by water-soluble sodium alginate, capable of forming viscous solutions. It is widely used to stabilize various solutions and suspensions. Adding a small amount of sodium alginate to food products - canned food, ice cream - improves their quality. It is also used to make decorative cosmetics, creams and masks in the perfume industry.

In the pharmaceutical industry, alginates are used to coat tablets, pills, as component bases for various ointments and pastes, as drug carrier gels, and in the production of soluble surgical sutures. In medicine, calcium alginate is used as a hemostatic agent and as a sorbent that removes radionuclides (for example, strontium). The annual production of alginates in the world exceeds 20 thousand tons.

Another important substance derived from brown algae is the six-hydric alcohol mannitol. Mannitol is used as a sugar substitute for diabetics. In addition, it can be used as a plasma substitute for blood conservation. It is used to make tablets in the pharmaceutical industry. Mannitol is also used in production of synthetic resins, paints, paper, explosives, leather dressing.

fucoidans, obtained from brown algae are effective anticoagulants, even more active than heparin. Their use for the production of antitumor drugs and antiviral compounds is considered promising. After all, even at the lowest concentrations, fucoidans can inhibit the attachment of viruses to the surface of cells. Fucoidans also have the ability to form exceptionally strong and viscous mucus, which is used in the preparation of stable emulsions and suspensions.

The energy crisis that has engulfed many countries of the world in recent years has led to the need to search for new non-traditional energy sources. So, in the USA, for this purpose, the possibility of breeding giant kelp algae is being studied. Macrocystis followed by processing it into methane. It has been calculated that from an area of ​​400 km 2 occupied by this alga, 620 million m 3 of methane can be obtained.

Heterocont algae from the classes Golden, Yellow-green, Sinura, Rafidophytes and Eustigma algae, represented mainly by microscopic organisms, are widespread in fresh water bodies of all climatic zones of the globe, but are more common in temperate latitudes. Among the golden algae, there are species that live in the seas and salt lakes, and very few in polluted waters. Golden algae reach their maximum development in the cold season: they dominate in plankton in early spring, late autumn and winter. At this time, they play a significant role as producers of primary production and serve as food for zooplankton organisms.

Some golden algae, for example Uroglena and Dinobrion, developing in mass quantities, they are able to cause water blooms. They release aldehydes and ketones, which can give water an unpleasant odor and taste, a Uroglena– fatty acids toxic to fish.

Rafid algae are widely represented in the plankton of fresh water bodies with predominantly acidic pH, especially in sphagnum bogs, less often in large lakes. In fresh water bodies, local "blooms" can form Goniostomum. Rafid algae are also found in desalinated sea bays and puddles on the seashore, as well as in the open sea. With mass development in coastal sea waters, they cause toxic "bloom" of water. So, off the coast of Canada during the "flowering" the concentration of cells of the rafid alga Heterosigma can reach 30 million per 1 liter. Outbreaks of raphid algae often lead to the development of "red tides", which are associated with the death of fish. The cause of such "red tides" may be species of childbirth Hattonella, Olistodiscus, Heterosigma and Fibrocapsa.

Sinura algae with mass development in fresh water bodies can give the water an unpleasant odor ( Sinura). Feotamnia algae are found in stagnant and slowly flowing fresh water bodies, where they settle epiphytically on filamentous algae.

Eustigma algae are found only in fresh water or in the soil.

Yellow-green algae are distributed on all continents, they live mainly in fresh water and soil, as well as in terrestrial, brackish water and marine habitats. Yellow-green algae inhabit clean and polluted waters, with different pH values: they can live in both acidic and alkaline waters. They are found mainly in clean freshwater reservoirs, less often in seas and brackish waters, preferring moderate temperatures, more often develop in spring and autumn, although there are species that occur throughout all periods of the year, including winter. Most often they can be found in clusters of threads and among thickets of higher aquatic plants in the coastal zone of rivers, ponds, lakes and reservoirs.

The vast majority of yellow-green are free-living forms, but there are also intracellular symbionts - zooxanthels in protozoan cells. An interesting intracellular symbiosis is formed by marine species chloroplasts Vosheri with clam Elision. For nine months, this mollusk is capable of photoautotrophic fixation of carbon dioxide in culture. This is the longest symbiosis of this type, when the symbiotic plastid is in direct contact with the cytoplasm of the animal. In nature, mollusk larvae feed on threads. Vosheri. As a result of phagocytosis, algal chloroplasts enter the cytoplasm of mollusk epithelial cells. During this process, the chloroplast membrane becomes three-layered, one outer membrane of the CES (chloroplast endoplasmic reticulum) is lost. This phenomenon is good evidence that, in the course of evolution, chloroplasts with three membranes could arise as a result of secondary symbiogenesis due to the loss of membranes.

Yellow-green, golden and other heterokont algae are producers of oxygen and organic substances; they are part of the food chain. Heterocontophytes are involved in the self-purification of polluted waters and soils, the formation of sapropel, in the process of accumulation of organic matter in the soil, affecting its fertility. They are used as representative organisms in determining the state of water pollution; yellow-green algae are part of a complex of microorganisms used for wastewater treatment.

test questions

Name the characteristic features of the structure of brown algae.

Structural features of brown algae thalli.

How do brown algae reproduce? What are monospores, tetraspores and zoospores, isogamy, heterogamy and oogamy?

What are the life cycles of brown algae? Reproduction of fucus and kelp algae.

Name the characteristic features and typical representatives of the orders of brown algae.

What habitats are brown algae found in? What is their significance in nature.

Economic importance of brown algae.

Name the characteristic features of the structure and typical representatives of golden algae.

What pigments and types of nutrition are known in golden algae?

Reproduction and ecology of golden algae.

Name the characteristic features and typical representatives of yellow-green algae.

What pigments and types of nutrition are known in yellow-green algae?

How do yellow-greens reproduce? Types of sexual reproduction: isogamy, heterogamy and oogamy?

Name the characteristic features of the structure and typical representatives of sinuric algae.

Reproduction and ecology of sinuric algae.

Name the characteristic features of the structure and typical representatives of pheotamnia algae.

Reproduction and ecology of feotamnia algae.

Name the general features of the structure and typical representatives of rafidophyte algae.

Reproduction and ecology of rafidophyte algae.

What are the common features of the structure and typical representatives of Eustigma algae.

Reproduction and ecology of Eustigma algae.

The value of heterocont algae in natural ecosystems.

Term protoctists proposed at the end of the 20th century. This kingdom includes eukaryotic relatively simple organisms. Among them: mushroom-like organisms - chytridiomycots, oomycots, slime molds, as well as algae (formerly lower plants) - green, brown, diatoms and others.

The main features of the representatives of this kingdom: more often live in the aquatic environment; unicellular, colonial or multicellular; the body is not divided into vegetative organs; reproduction is vegetative, asexual and sexual; in ontogenesis (individual development of the organism) there are no embryonic stages; nutrition is autotrophic and heterotrophic.

The mushroom-like organisms discussed below ( chytridiomycotes, oomycotes, slime molds) share features both with colorless flagellates (animals) and with colored algae. Until recently, these organisms were considered in the fungi kingdom ( Fungi) in the section of lower mushrooms.

mushroom-like protoctists Myxobionta

Department of Chytridiomycota(Chytridiomycota)

Figure 10. 1. A - "Black leg" cabbage, the appearance of a diseased plant (pathogen Olpidium brassicae), B - cabbage olpidium in the cells of the root neck of cabbage seedlings: 1 - zoosporangia, 2 - zoospores; 3 - naked protoplasts, 4 - resting spores.

Rice. 10. 2. A - potato cancer, the appearance of the lesion; B - synchytrium endobioticum: 1 - zoospores, 2 - summer cyst in the epidermal cell, 3 - beginning of cyst germination, 4 - disintegration into separate sporangia, 5 - copulation, 6 - winter cyst, 7 - cyst germination.

Department of Oomikota(Oomycota)

Rice. 10. 3. Potato mushroom (Phytophthora infestans): a, b - leaves and tubers of potatoes affected by late blight; c - mycelium and sporangiophores on a potato leaf; (d, e) exit of zoospores from zoosporangium; (f, g) zoospore and its germination; (h, i) conidia and its germination.

Department of slime molds (myxomycotta)(Myxomycota)

Rice. 10. 4.A - trichia (Trichia): 1 - appearance of sporulation, 2 - part of the capillium (special threads in sporulation, contributing to the scattering of spores) and spores; B– leocarpus (Leocarpus): 1 - appearance of sporulation, 2 - part of the capillary and spores.

Vegetative body of slime molds - plasmodium(mucous, non-shelled, multinucleated protoplasm), which has a variety of colors: pink, lemon yellow, red, purple, etc. Plasmodium moves slowly, like amoeba, absorbing and digesting bacteria, small fungi, particles of decaying plants and animals. Their sizes vary from a few millimeters to 1 m in diameter, but their weight is small - up to 20-30 g.

During the period of vegetative development, slime molds live in damp, dark places. They crawl out into the light to form fruiting bodies, sporangia and etalia, in which haploid spores are formed. The latter in water germinate into zoospores, and in a humid environment - into myxamebs. After a certain period of development, zoospores or myxamoebes copulate in pairs, forming diploid myxamoebes, which, by repeatedly dividing and growing, form plasmodium.

Seaweed - Thallobionta, or Algae

Seaweed- the oldest photosynthetic organisms on Earth, creating its oxygen atmosphere. Algae mainly live in the aquatic environment. About 30 thousand species of algae are known. Most of them live freely in the water column ( phytoplankton), some are attached to the bottom of water bodies or underwater objects, or simply lie on the bottom ( phytobenthos). Some algae live on the soil, in the soil or on tree trunks.

Algae are unicellular, colonial or multicellular, ranging in size from a few micrometers to 60-100 m with a very wide variety of body shapes.

Reproduction in algae is diverse: vegetative, asexual and sexual.

Vegetative reproduction is carried out by budding, cell division in two, fragments of filaments (in multicellular filamentous), disintegration of colonies and "nodules" (charophytes).

Asexual is carried out by spores: mobile (zoospores) or immobile (aplanospores). Spores are single-celled, formed in special organs - sporangia or inside vegetative cells.

Sexual reproduction is carried out by gametes, which are formed in special unicellular organs of sexual reproduction: oogonia (female gametangia) and antheridia (male gametangia). The essence of sexual reproduction is the fusion of gametes and the formation of a zygote. After a dormant period, the zygote germinates, producing zoospores or a new plant. In the development cycle of algae, the ratio of the diploid and haploid phases is different. If meiosis occurs during the germination of the zygote, then the alga is haploid throughout life, and the diploid phase is represented by the zygote. In some, the reduction division occurs in the gametangia before the formation of gametes, then the diploid phase predominates in their life cycle, and the haploid phase is represented only by gametes. This change of haploid and diploid generations is called the change of nuclear phases.

The forms of the sexual process are varied:

isogamy- fusion of morphologically identical motile gametes;

heterogamy- fusion of germ cells that differ in size and (or) mobility (behavior);

oogamy- fusion of gametes that differ sharply in shape, size and behavior; the female gamete is a large, immobile egg, the male gamete is a small, usually mobile, spermatozoon;

conjugation- fusion of the contents of two vegetative cells that physiologically perform the functions of gametes (Fig. 10. 5).

Rice. 10.5. Forms of the sexual process in algae: 1 - isogamy, 2 - heterogamy, 3 - oogamy, 4 - conjugation.

Large algae are used for food, as feed for farm animals, in medicine they serve as raw materials for the production of agar, alginates, and iodine. Some representatives are used in the process of biological wastewater treatment and as bioindicators of water pollution.

Depending on the biochemical characteristics (a set of pigments, the composition of the cell wall, the type of reserve substances), the following divisions of algae are distinguished: Red (Purple), Diatoms, Brown, Green.

Department Red Algae(crimson) - Rhodophycota

It has about 3800 species. These are mainly inhabitants of the seas, a small part is found in fresh water and in the soil. Among the purple ones there are immobile unicellular algae, filamentous and lamellar. Sizes from a few centimeters to 1-2 m (porphyry). The thallus of red algae is strongly dissected and looks like branched multicellular filaments attached to the substrate with the help of rhizoids. (Fig. 10. 6).

Rice. 10. 6. Red algae .

Chromatophores in the form of grains or plates contain pigments: red ( phycoerythrin), blue ( phycocyan), green ( chlorophyll).

Phycoerythrin dominates in deep-sea algae. It masks other pigments and gives a bright red color. Shallow water forms are bluish in color, as they are dominated by phycocyanins.

The product of photosynthesis is a polysaccharide purplish starch deposited in the cytoplasm. Cell walls, in addition to cellulose, are impregnated with a large amount of pectin substances, which are highly mucilaginous and swell, forming a soft or cartilaginous general frame, in which cell protoplasts are, as it were, immersed. Some crimson walls are saturated with calcium carbonate and magnesium.

Red algae reproduce asexually and sexually. Mobile (flagellar) stages during reproduction are completely absent. During asexual reproduction, sporangia are formed containing 1-4 passive spores. sexual process oogamous. female genital organ karpogon has an abdomen (expanded basal part), in which the egg and the process are located - trichogin. The male reproductive organ antheridium is a small, colorless cell that carries haploid sex cells - spermatozoa. The latter, having no flagella, are passively carried by currents of water and adhere to the trichogyne. At the point of contact, the dissolution of the walls of the spermatozoa and the trichogyne, the penetration of the spermatozoon nucleus into the abdominal cavity of the carpogon, and the fusion with the female nucleus are observed. After fertilization, a zygote is formed, and then diploid carpospores. Diploid thallus develops from carpospores, on which, as a result of reduction division, haploid thallus are formed. tetraspores. On the haploid thallus, developing from tetraspores, the genital organs are again formed, and the cycle repeats.

Sporophytes and gametophytes have a similar or different structure from each other.

Bagryanka– the best agaronoses(anfeltia - Ahnfeltia); having strongly mucilaginous pectin-cellulose walls. purple ( Porphyra) are used as food (in Japan, its industrial cultivation is developed). In some countries, scarlet is used for animal feed.

Department of Diatoms–Diatomophycota

It has more than 10,000 species distributed in the plankton of the seas, oceans and fresh waters, in the upper layers of the soil, in hot springs, in the snow. They are unicellular and colonial organisms. The cell protoplast is differentiated into cytoplasm, nucleus, and vacuoles. The reserve product of carbohydrate nature is chrysolaminarin. Chromatophores are large, lamellar or granular, yellowish-brown, contain chlorophylls, fucoxanthin and other xanthophylls (diatoms belong to the group of brown-colored algae). Instead of a cell wall, a thin bivalve shell is formed, consisting of silica. A large sash (epithec) is put on a smaller sash (hypoteca), like a lid on a box. Under the shell is a pectin wall (Fig. 10. 7).

Rice. 10. 7. Pinnularia (Pinnularia): a - view of the shell from the valve, b - view of the shell from the girdle, c - view of the algae from the valve, d - successive stages of cell division.

According to the shape of the cells, all diatoms are divided into two groups: centric (radially symmetrical) - mainly planktonic algae of the seas and oceans and pennate (bilaterally symmetrical) - more often freshwater benthic and ground algae.

Diatoms reproduce by longitudinal, most often vegetative cell division in two, followed by the completion of one leaf of the silicon shell - the hypotheca. The sexual process is isogamy and oogamy.

Diatoms live in a diploid state (i.e., the nuclei contain a double set of chromosomes), and only their gametes are haploid.

The role of diatoms in nature is great: they serve as the main food for a significant number of aquatic organisms (they have a high nutritional value); take a primary part in sedimentation (a huge number of shells of dead diatoms form diatom silts at the bottom of reservoirs).

Department Brown algae–Fucophycota

It contains about 1500 species, mainly growing in all seas. The size of these algae is from a few millimeters to 20-100 m. Tall has the form of either branched single-core and multi-core threads, or it has a complex structure (it is, as it were, divided into stem-like and leaf-shaped parts and has the beginnings of primitive tissue - assimilation, storage, mechanical and conductive ) (Fig. 10. 8).

Rice. 10. 8. Brown algae .

The main pigments in brown algae are: chlorophylls a and With, carotene, xanthophyll. The latter pigment gives the algae their characteristic brown color.

The cell walls consist of two layers: the outer mucilaginous, containing alginic acid, and the inner, formed by a variety of cellulose - alguose. The cells have one large nucleus, large vacuoles with cell sap and small vacuoles containing tannins, chromatophores in the form of disks or grains. Spare substances - laminarin, mannitol and, in a small amount, fats.

Reproduction of brown algae: vegetative (parts of thalli), asexual (zoospores) and sexual (isogamy, heterogamy and oogamy).

The best known genus of brown algae is kelp(laminaria)(Fig. 10. 9).

Rice. 10. 9. Laminaria (laminaria): a – general view of the sporophyte; b – section of a multicellular thallus with zoosporangia; c – zoospores; d - male gametophyte with antheridia; e - female gametophyte with oogonium.

Representatives of this genus (kelp sugar - Laminaria saccharina, kelp - L. digitata, Japanese kelp - L. japonica) form entire plantations in the northern and Far Eastern seas (in places with constant water movement, near open coasts). They are also known as "seaweed". Their thallus is divided into rhizoids, "stem" and "leaf" parts. The internal structure of the thallus is quite complex; differentiation into primitive tissues is noticeable. The thallus is perennial, the plate is replaced annually.

The thallus described is a diploid sporophyte. On the surface of the leaf plate of the sporophyte, single-celled zoosporangia are formed in groups, in which there are numerous zoospores. Zoospores are haploid and physiologically unequal. Germinating, zoospores give microscopic size gametophytes - outgrowths in the form of branching filaments, consisting of a small number of cells.

On the growths, organs of sexual reproduction are formed: female (oogonia) and male (anteridia). Antheridia are multicellular (a sign of higher organization). In gametangia, one gamete is formed (an egg and a sperm, respectively). After fertilization, a new diploid sporophyte grows from the zygote without a dormant period.

Laminaria is used: as food (diet food rich in iodine); for the production of medicines (contain iodine and polysaccharides, the concentration of iodine is at least 0.1%); to obtain algin polysaccharide (used as a gelling agent in the confectionery industry, in the manufacture of varnishes, paints); for animal feed; as a fertilizer (rich in potassium).

Department of Green Algae–Chlorophycota

The largest department, which has up to 20 thousand species. They live mainly in fresh waters and in the seas, some on snow, tree trunks and in the soil. In green algae, all types of thallus organization are represented: unicellular, colonial, multicellular filamentous and lamellar (Fig. 10.10).

Rice. 10. 10. Green algae.

Green algae contain pigments - chlorophylls a" and " in”, carotenes and xanthophylls (the last two pigments do not mask chlorophyll, and therefore algae are green in color). The reserve product is starch, which is deposited in the chromatophore around the pyrenoid. Chromatophores of various shapes: cup-shaped (chlamydomonas, chlorella), ribbon-shaped (spirogyra). In the stroma of chromatophores of green algae there is a light-sensitive eye - stigma. Cell walls usually contain cellulose and pectins. The endoplasmic reticulum is more developed than in other algae. All types of reproduction and all types of the sexual process are represented.

Department representatives:

Genus Chlamydomonas(Chlamydomonas) from the Volvox class - includes about 500 of the most primitive species of the green algae department. These include unicellular, round or pear-shaped, biflagellated, having a nucleus, cytoplasm, chromatophore with a pyrenoid; two pulsating vacuoles, a red eye orienting its movement under the action of light; wall consisting of pectin and hemicellulose. Capable of photosynthesis, but can consume ready-made organic matter. Most often found in polluted water (puddles, ditches). It reproduces vegetatively, asexually and sexually. Asexual reproduction is carried out by dividing the mother cell into 2, 4, 8 parts, from which zoospores are formed, which then turn into small vegetative individuals. During sexual reproduction, gametes are formed, when they merge, a zygote is formed, which hibernates, and in the spring divides and forms young individuals.

Chlorella (Chlorella) from the Chlorococcal class is a very widespread algae that is found in plankton and benthos of various water bodies, in moist soil, on tree bark and is a common symbiont of lichens. Chlorella is a single-celled algae of a spherical shape, devoid of mobility (passively carried by water currents). Its protoplast contains a bell-shaped chromatophore with a cavity containing a nucleus. Reproduction is only asexual, producing four or eight immotile spores.

Genus Ulotrix(Ulothrix) from the class Ulotrix includes 25 species that prefer fresh and brackish, clean water bodies. Ulothrix is ​​a green multicellular filamentous algae. The filament is unbranched, up to 10 cm long. The lowest cell of the filament is extended into a long colorless rhizoid (sole), with which the alga is attached to the substrate. The remaining cells are the same, each has one chromatophore with pyrenoids, a nucleus, a thin, sometimes mucoid, cellulose wall. Asexual reproduction is carried out by cell division into 2 or 4 four-flagellated zoospores that enter the water, attach to underwater objects, divide and form a filament of algae. During sexual reproduction (isogamy), small mobile gametes are formed that enter the water and merge in pairs. The resulting zygote is covered with a dense shell, under favorable conditions it is divided into 4 flagellate-free spores, which, attaching to underwater objects, divide, forming a thread of algae.

Ulva(Ulva) from the class Ulotriksovye is widely distributed along the coast of the southern and northern seas. Its thallus is multicellular, lamellar; plates of two layers of cells. At the base, the plate narrows into a short petiole with a sole, with which it is attached to a solid substrate. The ulva plate can easily break off and continue to live in this state. There are no specialized reproductive organs. Potentially, each cell can become a sporangium in a diploid generation, or a gametangium in a haploid one.

Spirogyra (Spirogyra) from the class Conjugates - a multicellular non-branching filamentous algae that forms the bulk of bright green ooze in ponds. The cells contain one nucleus, in the center there are vacuoles, in the parietal layer of the cytoplasm there are ribbon-like, spirally twisted chromatophores, along the midline of which pyrenoids are located, surrounded by starch grains. Vegetative reproduction - by scraps of threads, asexual reproduction - by immobile aplanospores, formed one in each cell. Sexual reproduction - conjugation: from opposite cells of two adjacent threads, processes grow that merge (the contents of one cell overflow into another), forming a zygote, after a dormant period, the contents of the zygote are divided twice, forming 4 cells, 1 of which grows into a new individual.

Caulerpa(Caulerpa) from the Siphon class - has a large thallus, dressed in a thick shell, there are no cell partitions; vacuole and parietal cytoplasm with numerous nuclei are continuous. Outwardly, siphons are similar to leafy plants. There is no asexual reproduction by zoospores; sexual reproduction occurs by the type of isogamy.

Vosheria(Vaucheria) from the Siphon class. This alga lives in moist soil, in fast-flowing and stagnant water bodies. Some species of this genus prefer brackish water. The thallus of the vosheria is unicellular, multinucleated, in the form of thin green creeping filaments. Chloroplasts are lenticular and fusiform, without pyrenoids. Spare oil. Reproduction is by fragments of filaments, asexually by polynuclear polyflagellated zoospores, aplanospores and cysts. The sexual process is oogamy.

Hara (Chara) from the Charovye class - found in fresh and brackish water bodies (but does not tolerate strong salinity). These are large, up to 50 cm and more, multicellular algae that prefer clean water bodies enriched with calcium salts. By its appearance, the hara resembles higher plants, in particular horsetails. The so-called stem is dissected into the so-called nodes and internodes, “leaves” depart from the nodes - whorls of short lateral branches, and is attached to the substrate by rhizoids. Chromatophores small, discoid. Vegetative reproduction - nodules, no asexual reproduction, sexual - oogamy. Sexual organs are multicellular. The genus Hara includes 40 species. Representatives of the Characeae are sometimes distinguished into a special department of the Characeae ( rice. 10. 11).

Rice. 10. 11. Chara algae.

Plant taxonomy deals with the study and description of plant species and their distribution into groups based on the similarity of the structure and family ties between them, the creation of a classification.

The main taxonomic categories in the classification of plants are species, genus, family, order, class, department, kingdom. Sometimes intermediate taxonomic categories are used: subspecies, supergenus, subkingdom, superkingdom, and others.

Table 1. Taxonomic categories and taxa on the example of potatoes:

Lower Plants, or Algae

General characteristics. Algae are a large group of photosynthetic, predominantly aquatic, photoautotrophic eukaryotic plants. Most algae are characterized by: mainly aquatic habitat, but a large number of species are also found on land (on the soil surface, wet stones, tree bark, etc.).

Most algae are suspended in the water column or actively swim ( phytoplankton), some lead an attached lifestyle ( phytobenthos). Green algae live in the coastal zone at shallow depths, brown algae contain pigments that allow them to live at a depth of up to 50 m, and a set of photosynthetic pigments of red algae allows them to live at a depth of 100-200 m, and some representatives are found at a depth of up to 500 m.

The body of algae can be unicellular, colonial or multicellular. If it is a multicellular organism, then its body is not differentiated into organs and tissues and is called thallus, or thallus. In complexly organized algae, elementary differentiation of the body can be observed, imitating the organs of higher plants - rhizoids, stem-like and leaf-like formations appear.

Cell structure. The cells of most algae have a cell wall formed by cellulose and pectin (only in primitive mobile unicellular and colonial algae, in zoospores and gametes, cells are limited only by the plasmalemma), the cell wall is almost always covered with mucus. The cell protoplast consists of the cytoplasm, one or more nuclei, and chromatophores (plastids) containing chlorophyll and other pigments; chromatophores have special formations - pyrenoids- protein bodies, around which starch is accumulated, which is formed during photosynthesis. Vacuoles are usually well developed; sometimes (especially in mobile cells) there are special contractile vacuoles; most mobile algae have flagella and a light-sensitive formation - an eye, or stigma, due to which algae have phototaxis(the ability to actively move the whole organism towards the light).

Reproduction is asexual and sexual, asexual reproduction carried out with the help of zoospores (mobile) or spores (fixed). Asexual reproduction can also be carried out using vegetative reproduction by fragmentation of the thallus, cell division of unicellular algae, in colonial algae - due to the collapse of colonies.

sexual reproduction occurs by the formation of many specialized sex cells - gametes and their fusion (fertilization), which is a sexual process. As a result of the fusion, a zygote is formed, which is covered with a thick protective shell. After a dormant period (less often immediately), the zygote germinates into a new individual, which is formed mainly by meiotic division (zygotic reduction). This completes sexual reproduction. Forms of the sexual process of algae - isogamy, heterogamy, oogamy. For some algae, the sexual process is carried out in the form conjugations. In highly organized algae, gametes develop in special organs of sexual reproduction: eggs - in oogonia, spermatozoa antheridia. In diploid algae, spore reduction Meiosis occurs when zoospores are formed, from which gametophytes. Gametophytes mitotically form gametes, and when a zygote is formed, a diploid algae is formed that forms spores - sporophyte. In haploid algae, spores and gametes can develop in the cells of the same individual, mitotically.

Origin of algae usually associated with the absorption by the eukaryotic aerobic cell of cyanobacteria, which became chloroplasts. Recently, a hypothesis has appeared that explains why chloroplasts in different divisions of algae differ sharply in structure and set of photosynthetic pigments - the ancestors of chloroplasts in different groups of algae may have been different photosynthetic bacteria. On the other hand, the same photosynthetic bacteria could be captured by different host organisms at different stages of evolutionary development. And the similarity of mitochondria in all eukaryotic organisms indicates that mitochondria originated from a single ancestor closest to the modern aerobic non-sulfur purple bacterium and the symbiosis of anaerobic heterotrophic prokaryotes and oxidizing bacteria developed before photosynthetic bacteria entered the symbiotic organism.

Red algae, or purple. One of the sub-kingdoms of the plant kingdom. Among the crimson, there are both unicellular and multicellular filamentous and lamellar algae (Fig.). Of the 4000 species, only 200 have adapted to life in fresh water and on the soil, the rest are inhabitants of the seas. The color of red algae is diverse, it is determined by the different quantitative content of pigments: chlorophylls a and d, carotenoids and phycobilins: red (phycoerythrin) and blue (phycocyanin). Moreover, the color of algae is different at different depths, in shallow water they are yellow-green, then pink, and at a depth of more than 50 m they turn red. The maximum depth at which crimson has been found is 500 m, where they use the blue-violet wavelengths of sunlight. The shorter the wavelength, the greater its energy, so light waves with the shortest wavelength penetrate to the greatest depth. Moreover, they seem black to divers, so effectively they absorb all the light falling on them, they look red on the surface. The pigments are concentrated in chromatophores, which look like grains or plates; there are no pyrenoids.

The cell wall is pectin-cellulose, capable of strong mucilage, as a result of which, in some algae, the entire thallus acquires a mucous consistency. In the walls of many, calcium carbonate (CaCO 3) or magnesium (MgCO 3) can be deposited.

The product of assimilation is purple starch, structurally similar to glycogen. Unlike ordinary starch, when stained with iodine, it acquires a brown-red color.

There is an alternation of sexual (haploid,n) and asexual (diploid 2n) generations. Asexual reproduction of red algae is carried out using haploid flagellated spores, developing meiotically in sporangia (spore reduction). Crimson is characterized by an oogamous sexual process.

Gametophytes develop from spores, gametophytes form non-flagellated male and female gametes. Most purples are dioecious plants. The zygote develops into a diploid sporophyte. Gametophyte and sporophyte are indistinguishable in appearance. Vegetative propagation by parts of the thallus is typical only for low-organized crimson.

Absence of flagellar forms- a characteristic sign of purple. It is assumed that the purple ones originated from eukaryotes that do not yet have flagella, on this basis they are distinguished into a separate sub-kingdom.

Bagryanki are of great practical importance. Agar-agar is obtained from them, which is used in the confectionery and microbiological industries, many of them are raw materials for the production of glue. Iodine and bromine are obtained from the ashes of scarlet. Some red algae are used for livestock feed. In Japan, China, on the islands of Oceania and in the USA, scarlet is used for food. Purple considered a delicacy. red algae chondrus used to obtain carrageenans - special polysaccharides that suppress the reproduction of the AIDS virus.

Department of brown algae. The department includes about 1500 species of multicellular, mainly macroscopic (up to 60-100 m) algae, leading attached ( benthic) Lifestyle. Most often they are found in coastal shallow waters of all seas and oceans, sometimes far from the coast (for example, in the Sargasso Sea).

Structure. The thalli of brown algae have the most complex structure among algae. Unicellular and colonial forms are absent. In highly organized cells, the thallus partly differentiates, forming tissue-like anatomical structures (for example, sieve tubes with oblique septa). As a result of this, the formation of “stem” and “leaf” parts of the thallus, which perform heterogeneous functions, occurs. In the substrate, algae are fixed with the help of rhizoids.

Brown algae cells are mononuclear with numerous chromatophores that look like discs or grains. The brown color of algae is due to a mixture of pigments (chlorophyll, carotenoids, fucoxanthin). The main storage material is laminarin(a polysaccharide with bonds between glucose residues other than that of starch), which is deposited in the cytoplasm. The cell walls are strongly mucilaginous. Mucus helps retain water and thus prevents dehydration, which is important for intertidal algae.

reproduction sexual and asexual. The forms of the sexual process are different - isogamy, heterogamy, oogamy. There is an alternation of asexual generation - sporophyte and sexual - gametophyte. The sporophyte and gametophyte may be the same or different in size and shape. Asexual reproduction occurs with the help of numerous biflagellate zoospores, meiotically formed in unicellular, less often multicellular zoosporangia of the sporophyte. on gametophytes ( n) oogonia and antheridia are formed, in which gametes are formed, a sporophyte develops from the zygote. Vegetative propagation is carried out by parts of the thallus.

Kelp. Representatives of the genus kelp are known under the name "sea kale" (Fig.). They are widely distributed in the northern seas. Mature laminaria sporophyte is a diploid plant from 0.5 to 6 meters or more in length.

The laminaria thallus has one or more leaf-like plates located on a simple or branched stem-like formation attached to the substrate by rhizoids. The stem-like formation with rhizoids is perennial, and the plate dies off annually and grows back in the spring.

Reproduction. On the surface of the plates, zoosporangia are formed, in which, as a result of meiotic division, haploid zoospores with two unequal flagella are formed. They germinate into microscopic filamentous gametophytes, on which the sex organs develop. The sexual process is oogamous. In oogonia and antheridia, one gamete is formed; after fertilization, a diploid sporophyte develops from the zygote without a dormant period. Thus, in kelp, alternation of generations is observed, the diploid sporophyte forms zoospores from which haploid gametophytes develop.

Typical representatives brown algae is kelp, macrocystis (its huge thallus reaches a length of 50-60 m), fucus, sargassum.

Meaning . Being autotrophs, algae are the main producers (i.e. producers) of organic substances in various water bodies. In addition, in the process of photosynthesis, they release oxygen, thereby creating favorable conditions for the life of not only aquatic, but also terrestrial organisms.

Algae play a huge role in human life: they are food for many commercial fish and other animals, serve as additives in various nutrient mixtures, are part of animal feed, some algae (for example, "seaweed") are eaten. Brown algae cells on top of the cellulose cell wall are covered with pectin, consisting of alginic acid or its salts, when mixed with water (in a ratio of 1/300), alginates form a viscous solution. Alginates are used in the food industry (for the production of marshmallows, marmalades), in perfumery (for the manufacture of gels), in medicine (for the manufacture of ointments), in the chemical industry (for the manufacture of adhesives, varnishes). In the textile industry, they are used to make colorfast and waterproof fabrics. Seaweeds are used to produce fertilizers, iodine, and bromine. Iodine was previously obtained exclusively from brown algae. Brown algae can serve as an indicator of the location of gold, they are able to accumulate it in the cells of the thallus.

Department of green algae. The department unites about 13,000 species; this is the most extensive department among algae. A distinctive feature is the pure green color of the thalli, caused by the predominance of chlorophyll over other pigments. Distributed everywhere. Mostly green algae are inhabitants of fresh water, but there are also marine species. Some live on land. There are species that enter into symbiotic relationships with some animals (sponges, coelenterates, tunicates) and fungi.

Structure . Green algae are represented by unicellular, colonial and multicellular forms. Cells have a dense cellulose-pectin membrane, they are single-nuclear or multi-nuclear. The cytoplasm contains chromatophores with pigments (mainly chlorophyll a and b,). In addition to chlorophyll, cells contain carotenoids, xanthophylls and other pigments. Chloroplasts are similar to the plastids of higher plants. The main storage substance that accumulates in chloroplasts is starch.

reproduction . Most green algae are haploid. The reduction of genetic material occurs after the formation of a zygote - zygotic reduction. But often there is a regular alternation of sexual and asexual generations.

Green algae are considered the ancestors of land plants: they have the same sets of photosynthetic pigments, the shell contains not only cellulose, but also pectin, the reserve substance is starch, reserve nutrients accumulate not in the cytoplasm (as in other algae), but in plastids.

Genus Chlamydomonas. In translation - a single organism, covered with ancient Greek clothing - chlamys. Unicellular algae, living mainly in shallow water bodies polluted with organic matter (Fig. 60). Chlamydomonas cell has a round or oval shape, the front end is pointed in the form of a spout. It has two flagella of the same size, with the help of which the chlamydomonas moves in the water. The cell wall is pectin-cellulose. In the center of the cell is a cup-shaped chromatophore with a large pyrenoid. The nucleus is located in the recess of the chromatophore. At the anterior end of the cell are the stigma and pulsating vacuoles.

Chlamydomonas reproduces both asexually and sexually. The life cycle is dominated by the haploid phase. During asexual reproduction, chlamydomonas loses flagella, the contents of the cell divide mitotically twice, and four daughter cells are formed under the membrane of the mother cell. Each of them secretes a shell and forms flagella, turning into zoospores.

Under the influence of enzymes, the shell of the mother cell is destroyed, and they go outside, grow to the size of the mother cell and also pass to asexual reproduction (Fig. 61).

The sexual process in many species of chlamydomonas occurs according to the type of isogamy. The content of the cell divides, forming from 8 to 32 gametes, which resemble zoospores, but are smaller. Cells with different sexes merge. The resulting zygote is covered with a thick shell and falls into a dormant period. When favorable conditions occur, the content of the zygospore divides meiotically, and four haploid cells are formed, each of which becomes a new chlamydomonas.

In some species, the sexual process is carried out according to the type of heterogamy (both gametes are mobile, but the female gamete is larger than the male one) or according to the type of oogamy (the female gamete is immobile).

Genus Chlorella. A unicellular alga that lives in fresh and salt water bodies, on moist soil, rocks (Fig. 62). Cells look like green balls up to 15 µm in diameter. It has no flagella, ocelli and contractile vacuoles. The cells have a cup-shaped chromatophore with or without a pyrenoid and a small nucleus. Chlorella uses solar energy much more efficiently for photosynthesis. If land plants use about 1% of solar energy, then chlorella - 10%. The sexual process for this algae is not known. Asexual reproduction occurs by mitotic division of the contents of the mother cell twice or thrice. As a result of division, four or eight immobile spores are formed ( aplanospores). After the rupture of the maternal membrane, the cells come out, increase in size and divide again.

Chlorella is interesting because its cells contain a large amount of nutrients - 50 complete proteins, fatty oils, carbohydrates, vitamins A, B, C and K, and even antibiotics (moreover, it contains 2 times more vitamin C than lemon juice). Nowadays, you can buy chlorella in an online store, for example, in this https://elitnie-chai.ru/superfood/chlorella.html. It multiplies so intensively that a thousand-fold increase in the number of its cells occurs per day.

Chlorella was the first algae that man began to grow in culture. It was used as an experimental object to study some stages of photosynthesis. In some countries (USA, Japan, Israel), pilot plants for growing chlorella have been created and the possibility of using chlorella as a source of nutrition for humans has been studied. The Japanese learned how to process chlorella into a white powder rich in proteins and vitamins. It can be added to flour for baking bakery products. In addition, chlorella is used as a source of cheap livestock feed and in biological wastewater treatment.

Class Ulotrix. Multicellular algae, the thallus of which is filamentous or lamellar. The most famous representatives belong to the genus Ulothrix and the genus Ulva. Non-branching threads of ulotrix, attaching to underwater objects - stones, piles, snags, etc., form green tufts. All cells (with the exception of a colorless rhizoidal cell elongated in length, with the help of which the alga is attached) have a similar structure. In the center of the cell is the nucleus and the chromatophore, which has the shape of an open ring. The chromatophore contains several pyrenoids. The growth of the thread in length occurs due to cell division in the transverse direction. It grows in fast-flowing rivers, leads an attached lifestyle (Fig. 65).

Under favorable conditions, ulotrix reproduces by zoospores that have four flagella. They are formed in an even number (2, 4, 8 or more). Zoospores come in different sizes - large and small. The ability to actively move zoospores contributes to the dispersal of ulotrix.

The sexual process occurs according to the type of isogamy. Individual cells of the thread turn into gametangia, in which biflagellated gametes are formed. The fusion of gametes results in a four flagellar zygote. Then she discards flagella and goes into a dormant state.

Subsequently, the zygote undergoes reductional division, giving rise to four cells, each of which forms a new thread.

An important evolutionary line is associated with the transition from a filamentous thallus to a lamellar one. It is this form of thallus in representatives of the genus Ulva (sea lettuce). Outwardly, the ulva resembles a thin green sheet of cellophane, its thallus up to 150 cm consists of two layers of cells. Ulva is characterized by alternation of generations, and the diploid sporophyte and haploid gametophytes do not differ externally. This alternation of generations is called isomorphic.

The genus Spirogyra. Green filamentous algae up to 8-10 cm long (Fig. 63). Numerous species of spirogyra live in fresh water, in stagnant water. Accumulations of filaments of spirogyra form mud. Filaments unbranched, formed by one row of cylindrical cells. Flagellar stages are absent.

In the center of the cells is a large nucleus. It is surrounded by cytoplasm, diverging in the form of strands from the center of the cell to the periphery. Here they are connected to the parietal layer of the cytoplasm. The strands pierce a large vacuole. The cells contain ribbon-like, spirally twisted chromatophores. They are wall-mounted on the inside of the shell. In different species of spirogyra, the number of chromatophores ranges from 1 to 16. Large colorless pyrenoids are located in large numbers in the chromatophores. Outside, the algae is surrounded by a mucous membrane.

Rice…Staircase conjugation of spirogyra

Algae growth in length is carried out by transverse cell division. Spirogyra reproduces asexually and sexually. Asexual reproduction is carried out by parts of the threads when they are accidentally broken.

The sexual process is carried out by conjugation (Fig. 64). Conjugation can be ladder and side. With ladder conjugation, two strands are parallel to each other. In adjacent cells, they form dome-shaped outgrowths growing towards each other.

At the point of contact, the partitions separating the cells dissolve, and a channel is formed that connects both cells. The content of one cell (male) is rounded and flows through the tube into another (female), and their content (primarily the nucleus) merges. With lateral conjugation, fertilization occurs within one thread. In this case, the fusion of protoplasts of two adjacent cells is observed.

The zygote formed as a result of fertilization is surrounded by a thick cell wall and falls into a dormant period. In spring, the zygote undergoes reductional divisions and forms four haploid nuclei. Three nuclei degenerate, and the fourth divides mitotically and gives rise to a new haploid filament. Thus, spirogyra goes through the life cycle in the haploid phase, only the zygote is diploid.

Key terms and concepts

1. Systematics of plants. 2. Phytoplankton, phytobenthos. 3. Thallus, thallus. 4. Phototaxis. 5. Crimson starch. 6. Pyrenoids. 7. Gametophyte and sporophyte of laminaria. 8. Laminaria. 9. Chlorella, chlamydomonas. 10. Aplanospores. 11. Ulothrix, Ulva. 12 Isomorphic alternation of Ulva generations. 13. Spirogyra

Essential Review Questions

1. The main taxonomic categories used in the classification of plants.
2. Crimson characteristics.
3. characteristics of brown algae.
4. The value of brown algae.
5. Characteristics and representatives of green algae.
6. Reproduction of chlamydomonas, chlorella.
7. Reproduction of ulotrix, spirogyra.
8. Ulva reproduction.

The textbook is written in accordance with the requirements of the Federal State Educational Standard of Higher Professional Education in the direction of "Pedagogical Education" and complements the knowledge of students in the theoretical part of the course "Botany" (systematics of plants and fungi). The material of the manual can be used by students both for independent work and for work in the classroom under the guidance of a teacher.

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The following excerpt from the book Botany. Plant Systematics: a textbook (S. K. Pyatunina, 2013) provided by our book partner - the company LitRes.

Seaweed (algae)

A large and diverse group of lower thallus plants whose primary habitat is water. Algae unite several independent and, in all likelihood, independently evolved departments. Representatives of the departments differ in the set of pigments, details of the fine structure of chromatophores, in the products of photosynthesis that accumulate in the cell (reserve substances), and in the structure of the flagellar apparatus. Lower plants are unicellular, colonial or coenobial and multicellular organisms. Colonies are called cenobia, in which the number of cells is determined in the early stages of development and does not change until the next stage of reproduction (reproduction). The growth of coenobia occurs due to an increase in the size of cells, and not their number. There are the following types of morphological organization of the thallus:

1. Monadic- cells that actively move with the help of flagella.

2. coccoid- immobile cells.

3. rhizopodial (amoeboid)- vegetative cells are not covered with membranes and can develop cytoplasmic processes - rhizopodia.

4. palmelloid, or capsal, the type of organization is represented by immobile cells immersed in a common mucus.

5. filamentous- cells connected in threads, simple or branched.

6. heterotrichous, or multifilamentous,- a complicated version of the filamentous structure, which is characterized by two systems of threads: creeping along the substrate and vertical threads extending from them.

7. lamellar- thalli in the form of plates.

8. Siphonal- thalli, often large, formally represent one cell, usually with a large number of nuclei.

9. siphonocladal the organization is represented by multinuclear cells connected in filamentous or other forms of multicellular thalli. At the first stages of thallus formation, it has a siphonal type of structure.

Algae can reproduce in three ways: vegetatively, asexually and sexually. Vegetative propagation consists in separating a part of the vegetative thallus from the whole plant, giving rise to a new thallus. Asexual reproduction is carried out with the help of specialized cells - dispute, produced in sporangia. Spores are mobile (zoospores) or motionless (aplanospores). They may be identical in shape to the parent thalli. (autospores unicellular algae) or differ sharply from them (unicellular spores of multicellular algae).

Sexual reproduction in algae is extremely diverse. The simplest forms of the sexual process - the fusion of morphologically indistinguishable vegetative individuals - hologamy and conjugation. In a significant part of algae, the formation of specialized germ cells - gametes. The following behavior of hemets is distinguished:

1. Isogamy - fusion of gametes of the same size and shape.

2. Heterogamy - both types of copulating gametes have flagella, but the female is larger and less mobile than the male.

3. Oogamy - fusion of an immobile female egg and a mobile male cell. Copulate gametes that have arisen on the same individual (homothallism) or on different individuals (heterotallism). Heterotallism is observed in any form of the sexual process. In isogamous forms, gametes with morphological identity turn out to be physiologically different and are designated by the conventional signs "+" and "-". Male gametes that have flagella are called spermatozoa, not having flagella, but able to move with the help of amoeboid movements are called spermatozoa. As a result of the sexual process, a diploid cell is formed - zygote.

Life cycle, or algae reproduction cycle, includes vegetative growth, asexual sporulation, sexual process, resting stages. The ratio of diploid and haploid phases in the life cycle of algae is not the same. In some cases, the germination of the zygote is accompanied by a reduction division (meiosis) of the zygote. (zygotic reduction), while developing plants are haploid. In many green algae, the zygote is the only diploid stage in the development cycle; the entire vegetative phase passes in the haploid state. This life cycle is called monohaplobiont. In some other algae, on the contrary, the entire vegetative phase is diploid, the haploid phase is represented only by gametes, before the formation of which the reduction division of the nucleus occurs. (gametic reduction), life cycle - monodiplobiontic. In still others, the reduction division of the nucleus precedes the formation of spores that develop on diploid thalli. (sporic reduction). They grow into haploid sexually reproducing plants. (gametophytes). After the fusion of gametes, the zygote develops into a diploid plant, bearing organs of asexual reproduction ( sporophytes). Thus, these algae have an alternation of generations (generations): diploid and haploid. Life cycle - haploid-diploid. Both generations may be morphologically the same ( isomorphic change of generations) or drastically different in appearance (heteromorphic change of generations).

In practical classes, they study the departments: green (Chlorophyta), diatoms (Bacillariophyta or Diatomeae), brown (Phaeophyta), red (Rhodophyta) algae.

Department of Green Algae (Chlorophyta)

The Department of Green Algae is the largest in terms of the number of species (up to 20,000 species) and morphologically diverse department of algae. There are also microscopic small, unicellular forms (monadic and coccoid) and rather complexly arranged filamentous, heterotrichous, siphonal, siphonocladal and lamellar forms, reaching several tens of centimeters. The area of ​​distribution of green algae is also extensive (they are found all over the globe) and their ecological amplitude is wide. They live in fresh and marine waters, some live out of water. But with all the diversity, green algae have a number of common features:

1) pigment composition: chlorophyll a and in, carotenoids and xanthophylls;

2) the main reserve product of a carbohydrate nature, starch, is deposited in the chromatophore around the pyrenoid;

3) photosensitive eye - stigma, located in the stroma of the chromatophore;

4) thylakoids bearing pigments tend to stack;

5) flagella are isomorphic (same in structure) and isocontoid (equal in length).

Class Actually green, or equal flagella, algae (Chlorophyceae, Isocantae)

Representatives of this class are characterized by asexual reproduction with the help of immobile aplanospores or mobile zoospores with two to four, less often many isocont and isomorphic flagella. Sexual processes - chologamy or copulation of gametes - isogamy, heterogamy, oogamy. The zygote usually goes through a dormant state and germinates when favorable conditions occur, and its diploid nucleus immediately divides by reduction. In accordance with the steps of morphological differentiation of the thallus, the class is divided into orders.

Order Volvox (Volvacales)

The order includes unicellular, colonial and coenobial algae equipped with flagella, that is, a monadic organization.

Genus Chlamydomonas (Chlamydomonas)

Chlamydomonas is an extensive genus of about 500 species, widely distributed in nature. Its species can be found in shallow, well-heated reservoirs, puddles, ditches. With mass development, it causes flowering of water, especially in reservoirs polluted with organic substances. The thallus of chlamydomonas is unicellular, of a monadic organization, that is, being in an active state, chlamydomonas quickly move with the help of two equal flagella attached to the anterior end of the body. The phase of active movement is replaced by a state of rest. This is the so-called palmelle-like stage, when the cells lose their flagella, their membranes become strongly mucilaginous and form aggregations of Chlamydomonas cells immersed in the common mucus. In this form, chlamydomonas cells multiply by division. Getting into favorable conditions of existence, chlamydomonas again produce flagella and move on to active movement.

Chlamydomonas has a cellulose-pectin cell membrane, a cup-shaped chromatophore with one or more pyrenoids located in the lower part, and a light-sensitive eye (stigma) in the upper part. The nucleus is located in the deepening of the chromatophore, there is a pair of pulsating vacuoles. Asexual reproduction by zoospores occurs in favorable habitat conditions. Each Chlamydomonas can potentially reproduce both vegetatively and asexually, as well as participate in the sexual process. During asexual reproduction, the protoplast divides into 4 or 8 parts, zoospores are formed. The sexual process in most species is isogamous. Gametes are formed in the same way as zoospores, but in larger numbers (32 or 64). The zygote is well adapted to endure adverse conditions. Its germination is accompanied by reduction division. The development cycle of chlamydomonas is monohaplobiont.

Rod Volvox (Volvox)

The genus Volvox is a colonial or coenobial algae. A small genus of Volvox lives in clean standing water, ponds and small lakes. This is the most highly organized representative of the Volvox order. It is a large ball, reaching 2–3 mm in diameter, covered with a thin layer of mucus (involucrum), under which biflagellated cells are located in one layer along the periphery of the ball. Their number ranges from 500 to 60,000. The inner cavity of the ball is occupied by liquid mucus. The cells of the colony are similar in structure to the cells of chlamydomonas. But the shell of each cell is strongly mucus, so the protoplasts of neighboring cells are distant from each other and the cytoplasmic processes penetrate the thickness of the mucus membrane. Plasmodesmata are formed at the points of contact.

In asexual reproduction, 8-10 cells are involved, located in the back, relative to the direction of movement, part of the sphere. These are gonidia. Among others, these cells are distinguished by larger sizes. When they divide, a flat 16-cell plate (gonic stage) is first formed, further division leads to the formation of an open sphere with a small open hole directed towards the outer surface of the parent colony. The forming cells of the new organism are turned with their flagella into the sphere. The normal orientation of the cells (with the anterior ends directed outward) is achieved by completely turning the open sphere inside out, only after that its opening closes. Reproductive cells differentiate very early, so that not only daughter colonies, but granddaughter colonies can be observed inside the maternal organism. Young colonies are released after the destruction of the mother colony.

Cells that serve for sexual reproduction are oogonia and antheridia. Dark green oogonia are much larger than other cells and lack flagella. One large egg develops in the oogonium. Antheridia form packets of spermatozoa. The sexual process in Volvox is oogamous. There are bisexual and dioecious species, as well as homo- and heterothallic clones. A resting zygote is formed, which germinates as a young daughter colony after the reduction division of diploid nuclei. The development cycle is monohaplobiont.

Objects: r. chlamydomonas, r. volvox.

Progress

1. Consider chlamydomonas first at low magnification (m. magnified), then in more detail at high magnification (b. magnified), study immobile individuals, observe the movement of chlamydomonas.

2. Make two drawings:

a) the appearance of chlamydomonas. Designate the shell, chromatophore;

b) a diagram of the structure of the chlamydomonas cell, using the table. Designate the membrane, cytoplasm, nucleus, chromatophore, ocellus (stigma), pyrenoid, flagella, pulsating vacuoles.

3. Consider at m. and sketch spherical coenobia of volvox with daughter colonies from the preparation.

4. Make a schematic drawing using the table, reflecting the structural features of the coenobia. Name the protoplasts, cytoplasmic processes, plasmodesmata, flagella, oogonia, antheridia.

Order Chlorococcal (Chlorococcales)

The order includes unicellular and coenobial forms with coccoid cell organization.

Genus Chlorococcus (Chlorococcus)

The genus Chlorococcus contains 38 species and is found in a variety of habitats: in water, both in plankton and in benthos; in the soil, as well as on the bark of trees, on old wooden buildings. Chlorococcus is a part of lichens.

It is a unicellular coccoid algae, immobile in the vegetative state. The cells have a cupped chromatophore with a pyrenoid, but lack flagella, ocelli, and pulsating vacuoles. The nucleus is located in the recess of the chromatophore. In old individuals, several nuclei can be observed, the cells are covered with a thick cellulose membrane.

Chlorococcus reproduces asexually with the help of elongated biflagellate zoospores. The protoplast of the mother cell divides and forms from 8 to 32 zoospores, which are released after the destruction of the wall of the mother cell. The period of active movement is short; after swimming for some time, zoospores lose their flagella, dress in a shell, grow, reaching sizes characteristic of a particular species. The sexual process is isogamous. The development cycle is monohaplobiont.

Genus Hydrodition (Hydrodiction)

Hydrodition is a small but widespread genus. It is found in backwaters of rivers, ponds and other stagnant water bodies enriched with nitrogen. This is a macroscopic coenobial alga, composed of a large number (up to 20,000) of cells. Old specimens reach a meter in length, and their cells are up to one and a half centimeters.

Hydrodiction looks like a closed network, consisting of 5-6-sided cells formed by giant cells connected at their ends. Adult reticulum cells contain one giant vacuole, the cytoplasm is parietal and contains a reticulate chromatophore with numerous pyrenoids and a large number of small nuclei. The shell is cellulose. Each cell performs all the functions of the body (nutrition and reproduction).

Reproduction of the water mesh is asexual and sexual. Cells that have already reached a sufficiently large size (0.2 mm) begin asexual reproduction. In the protoplast, such a number of zoospores is formed that is characteristic of this type of reticulum. Zoospores do not leave the mother cell, but move inside the cell for some time.

Then the flagella are shed and folded into a young mesh, sticking together with each other in those places where the strands of microtubules pass. The cells of the young reticulum are mononuclear, with a lamellar chromatophore bearing one pyrenoid. For some time, the young mesh lives under the shell of the mother cell, but its size rapidly increases, the cells are elongated. In the end, the shell of the mother cell is destroyed, and the reticulum begins to live independently.

Sexual reproduction is isogamous, gametes are formed more than zoospores, and they are much smaller. The zygote is stained with hematochrome brick red. After a dormant period, the zygote divides by reduction and germinates into four large zoospores. They are inactive, soon lose their flagella and again become covered with a thick, but already sculptural shell, turning into the so-called polyhedron Polyhedra, the shells of which have processes, and the contents are rich in fatty inclusions, apparently, are important for the distribution of algae. Polyhedra can tolerate desiccation well and are thus the second dormant stage in the water network development cycle.

Genus Chlorella (Chlorella)

Chlorella is a very widespread algae. In nature, it is found in plankton and benthos of various water bodies, on the soil, participates in the formation of the body of lichens, and also lives in symbiosis with small animals, forming the so-called zoochlorella. It is one of the cultivated algae. Due to the high reproduction rate, chlorella gives a high biomass yield.

Chlorella is a single-celled spherical coccoid algae. The protoplast contains a bell-shaped chromatophore with a large depression. In the cavity of the chromatophore, a nucleus can be found. Chlorella reproduces only asexually by autospores. The sexual process is unknown. The development cycle is asexual, monohaplobiont.

Objects: r. chlorococcus, r. water mesh, r. chlorella.

Progress

1. Consider at b. led away. and draw chlorococcus. Designate a thick shell (an adaptation to an aerophilic lifestyle), a cup-shaped chromatophore.

2. Consider at m. a fragment of the coenobium of the water mesh and draw, showing 5-6-angled cells that form the coenobium. Designate the cell of coenobia, chromatophores.

3. Consider at b. led away. and draw a cell of a coenobium with a young coenobium inside the cell. Designate the shell of the mother cell, the young coenobium.

4. Sketch chlorella at b. led away. Name the thick shell, chromatophore.

Order Ulotrix (Ulothrichales)

The order combines algae that have a thallus in the form of an unbranched thread, composed of mononuclear cells, less often a lamellar or tubular thallus.

Rod Ulotrix (Ulothrix)

Ulothrix is ​​a fairly large genus, found in fresh and slightly brackish water bodies, prefers clean running water. In the coastal zone of rivers and streams, especially in areas with a suitable climate, Ulothrix zonata can be found. Ulothrix is ​​a benthic, attached algae that forms aggregations on coastal rocks.

Ulothrix is ​​a multicellular, filamentous, unbranched algae. All cells, with the exception of the basal, which serves for attachment, are of the same type. They are covered with a thin, sometimes mucilaginous, cellulose membrane. The chromatophore is parietal in the form of a closed or open belt with a large number of pyrenoids. There is only one nucleus in the cells. The number of cells in the filaments is indeterminate, since in the upper parts of the cells they are constantly dividing in the same plane. Ulothrix reproduces vegetatively (by fragmentation of the thread), asexually and sexually. Asexual reproduction is carried out by zoospores, equipped with four isocont and isomorphic flagella. Zoospores, germinating, form ulotrix filaments. Any but the basal cell of the filament can potentially become a zoosporangium. Ulothrix forms biflagellated isogametes. After the fusion, a planosygote is formed (a mobile cell with four flagella), which then loses the flagella and differentiates into a unicellular peculiar sporophyte - an expanded, thick-shelled body on a thin stalk. The zygote-sporophyte stays in such a resting state for some time, and then, after reduction division, 4-16 zoospores are formed in it. Such a life cycle is characteristic of Ulothrix zonata. In some species, the zygote grows into a diploid filament. Thus, the cycle of development in Ulothrix zonata is with a heteromorphic change of a multicellular filamentous haploid sporogametophyte and a unicellular diploid sporophyte.

Rod Ulva (Ulva)

The genus Ulva is known as "Sea Lettuce" and is widely distributed but prefers shallow waters. Ulva is a seaweed, but it tolerates desalination well. It lives in estuaries, shallow estuaries, marshes; well tolerates, and partly prefers waters with significant organic pollution. The local population uses it for food, but the ulva has no commercial value.

The ulva thallus is multicellular, lamellar, consists of two layers of cells, the edges of the plate are corrugated due to more intense cell divisions in the marginal, compared with the median, zones. At the base, the plate narrows into a short petiole with a sole, with which it is attached to a solid substrate. Cell differentiation in the ulva thallus is low. There are no special reproductive organs. Potentially, each cell can become a sporangium in the diploid generation or a gametangium in the haploid one. Some cells have tubular outgrowths descending along the central part of the thallus.

Asexual reproduction is carried out by four-flagellated zoospores, which are formed on diploid plants after reduction division. Zoospores germinate into a single-row non-branching thread, but even before the start of division, polarization is detected in the zoospore that has lost flagella and settled on the ground. The upper end is thicker, while the lower end is thin and elongated, from which attachment structures are subsequently formed. The sexual process is iso- or heterogamous, the gametes are biflagellated. The cycle of development is haplodiplobiont with an isomorphic change of generations.

Objects: r. ulotrix, r. ulva.

Progress

1. Consider at b. led away. and draw a section of the ulotrix filament, pay attention to the structure of the chromophore. Label the cells of the thallus: cell membrane, chromatophore, pyrenoids.

2. Sketch the appearance of the ulva thallus using a wet preparation.

Chaetophore order (Chaetophorales)

The order includes multicellular filamentous forms of the heterotrichous type with differentiation of the thallus into a horizontal, spread over the substrate, and a vertical system of filaments.

Rod Draparnaldia (Draparnaldia)

Species of this genus are demanding on cleanliness and aeration of reservoirs and prefer fast-flowing rivers and streams. They grow en masse at fairly significant depths (10 m), forming whole thickets there. Draparnaldia benthic is an attached algae of a filamentous heterotrichous structure. It has long (unlimited growth) weakly branching filaments with a girdle-shaped chromatophore with jagged edges. The chromatophore in such branches is small relative to the total volume of the cell, so the cells of the main filaments are pale. Bundles of short highly branched branches of limited growth depart from these threads in whorls, these are assimilators. The chromatophores in them are parietal, large; green cells. Each short thread ends with a colorless long hair. The reproductive organs are placed among the assimilators. Asexual reproduction by four flagellar zoospores. The sexual process is isogamy or heterogamy. The development cycle is monohaplobiont.

Genus Trentepolia (Trentepohlia)

Trentepolia is an aerophilic terrestrial alga, well adapted to the lack of moisture. She settles on the bark of trees, stones, wooden buildings. Especially many species of this genus are found in humid tropical and subtropical regions, where trentepolia often leads an epiphytic lifestyle. Trentepolia is easy to recognize among other terrestrial algae due to hematochrome, an oil-soluble carotenoid that gives it a brick red or yellow color. The thallus of trentepolia is filamentous, heterotrichous. The filaments that creep along the substrate consist of rounded or oval cells covered with a thick layered membrane. They are connected to each other by pores with plasmodesmata, but, nevertheless, the creeping filaments easily disintegrate into short fragments or individual cells. These fragments and cells in the dry state are dispersed and carried by the wind. Thus, trentepolia has a fairly effective mechanism of vegetative reproduction, which is especially important in conditions of water deficiency. The cells contain several disc-shaped or ribbon chromatophores devoid of pyrenoids and a large number of nuclei, especially in old cells. In addition to the horizontal, there is a system of vertical threads, consisting of more elongated cells. Both horizontal and vertical filaments branch profusely due to the division of apical cells; layered caps form on the latter.

Asexual reproduction occurs by two- or four-flagellated zoospores, which are formed in special apical cells - sporangia, sitting on tubular cells - legs. The sporangia are detached and carried in their entirety by air currents. Zoospores are formed only if the sporangium is in the water. Then the multinuclear content very quickly, in a few minutes, breaks up into single-nuclear sections, and zoospores are produced. Gametangia also differ morphologically from vegetative cells, but are located mainly on creeping filaments. Unlike sporangia, globular gametangia do not have legs. Gametangia are also carried by air currents. Once in the water, they germinate with biflagellate isogametes. However, copulation is rare, and gametes develop parthenogenetically (without fertilization). In the case of the formation of zygotes, they germinate as zoospores after a dormant period. The development cycle is monohaplobiont.

Objects: r. draparnaldia, r. trentepoly.

Progress

1. Consider at m. and draw a section of the heterotrichal filamentous thalom of Draparnaldia, note the structural features of the “stem” filaments and assimilators, show the difference in the structure of chromatophores in the cells of the axial filament and in the cells of the lateral branches. Designate the axial thread, assimilator threads.

2. Consider at b. led away. and draw the cell of the axial thread and the cell of the assimilator thread. Label the cell wall, the chromatophore.

3. Consider at b. led away. and sketch a section of the trentepoly thread. Designate the layered membrane, reserve substances (in the form of oil drops stained with hematochrome), disk-shaped chromatophores.

Order Cladophoraceae (Cladophorales)

The order includes non-cellular algae, filamentous branched, divided by transverse partitions into unequal segments, each of which contains many nuclei. Transverse partitions arise independently of nuclear fission.

Genus Cladophora (Cladophora)

Cladophora is a very large and widespread genus of mainly marine and partly freshwater algae. About 150 species have been described. It occurs in shallow waters in the surf zone, on rocks protruding into the sea, in lagoons, ponds, lakes. Young plants are attached to the ground or to various underwater objects, but later break off and swim, forming large clusters or hard mud; as well as large (10–15 cm in diameter) globular clusters. The thallus is highly branched, with a siphon-clad structure. The segments formed by the transverse partitions are not cells in the true sense. The formation of transverse septa is qualitatively different from cytokinesis and is not associated with nuclear fission. The segments are unequal in size and contain a different number of cores. The mesh chromatophore is also formed by contact and fusion of initially free chloroplasts. The outer shell is thick, cellulose, never mucus, so Cladophora mud is tough and not slippery.

Reproduction is asexual and sexual. Any segment of the alga can become zoosporangium or gametangium. Tetraflagellated zoospores emerge from the sporangium through a pore and germinate first into a vesicular body devoid of septa (siphonal stage), later transverse septa appear and branching of filamentous structures occurs. The sexual process is isogamous. The zygote grows into a diploid plant. Most species of cladophores living in the seas have an isomorphic change of generations, in which case zoospores are formed after reduction division (meiozoospores), but freshwater species have a monodiplobiont cycle, when reduction division precedes the formation of gametes.

Objects: r. cladophora.

Progress

Consider at b. led away. and draw a section of the branching thallus of the cladophora with zoosporangia. Designate thallus cells, unicellular zoosporangia.

Class Conjugates (Conjugatophyceae)

Representatives of this class have a special type of sexual process - conjugation, there are no flagellar stages, there is no asexual reproduction by spores.

Zignemov order (Zygnematales)

Order Zignemovye - filamentous unbranched multicellular algae, their shell is mucilaginous, and therefore they are slippery to the touch. The zygote germinates as one seedling, the other three nuclei formed in the process of reduction division die off.

Genus Spirogyra (Spirogyra)

The genus Spirogyra is one of the largest and most widespread around the globe: it is found even in Antarctica. A rare ditch, puddle, pond or lake is devoid of mucous to the touch, floating on the surface of mud. The spirogyra thallus is filamentous, unbranched, all cells in the filament are equivalent and of the same type. The cell has one or more parietal, spiral, ribbon-like chromatophores, with a large number of pyrenoids located along the longitudinal axis. The edges of the chromatophore are uneven. The cell has one or more vacuoles with cell sap. In the first case, the cytoplasm occupies a lean position. In the presence of several vacuoles, in addition to the parietal layer of the cytoplasm, there are cytoplasmic cords and a central cytoplasmic sac, in which there is a large, clearly visible without color, nucleus. The inner layer of the cell membrane is cellulose, the outer layer is pectin, which provides mucus and the formation of a gelatinous cover, which gives the threads a silkiness. In spirogyra, living in reservoirs with a strong current, various kinds of rhizoids are produced that hold the algae in place. Spirogyra, like other conjugates, does not have a flagellar stage in the development cycle and does not form spores. It reproduces either by fragmentation of threads vegetatively or sexually. During conjugation, numerous zygotes are formed, which, after a dormant period, germinate with one thread. Of the four haploid nuclei formed in the process of reduction fission, three small ones die off, and one large viable nucleus remains. All the nutrients accumulated in the zygote go to the formation of one seedling. Zygotes are well adapted to endure adverse conditions. They are covered with a thick three-layer sculpted shell. The structure of the zygote shell is an important taxonomic feature.

Objects: r. spirogyra.

Progress

Consider at m. and sketch the appearance of the multicellular thallus of Spirogyra. Label the thallus cell.

1. Consider at b. led away. and draw a spirogyra cage. Name the cell membrane, chromatophore, pyrenoids,

nucleus, strands of cytoplasm.

2. Observe and draw the different stages of the conjugation process.

Designate the stages: formation of conjugative processes, contraction and overflow of the protoplast, formation of the zygote.

Order Desmidia (Desmidiales)

Order Desmidia - unicellular organisms or filamentous colonies. The cell consists of two equal halves - semi-cells. During vegetative propagation, each semi-cell completes the construction of the second half.

Rod Closterium (closterium)

Klosterium is a freshwater benthic algae that requires good lighting, it lives in small reservoirs, ponds, quiet backwaters of rivers and in fouling of underwater objects. With mass development, mucous accumulations are formed. Klosterium loves clean water, but tolerates organic pollution, and is sometimes found in wastewater. This is a unicellular form, its sickle-shaped body consists of two symmetrical halves - semi-cells. The nucleus is located in the center, in the cytoplasmic sac. The closterium does not have an external constriction characteristic of other desmid algae, but the internal structure corresponds to the features of representatives of this order. Closterium has two identical axial chromatophores, a peculiar structure. Several plates extend radially from the central rod so that the chromatophore looks like a multi-beam star in a cross section. Large pyrenoids are located along the shaft or randomly scattered at the base. The base of the chromatophore, facing the center of the cell, is wide; at the ends of the cell, the chromatophore narrows conically. At the poles of the cell there are two small vacuoles with cell sap, in which small crystals of gypsum are immersed, which are in constant motion (Brownian motion), and special mucous bodies. The three-layer shell of the closterium is permeated with numerous conical pores. Particularly large pores are located at the ends of the cells. These pores secrete mucus, thanks to which the alga moves slowly. While one end of the body is attached to the substrate, the other end oscillates. The algae is then attached to the substrate with the other end. So tumbling, the closterium moves towards the light source.

Closterium reproduction is vegetative. Cells divide transversely. Each daughter cell receives half of the mother cell with one chromatophore. The second half, that is, the half-cell, is being completed anew. First, the young semi-cell does not have a chloroplast, and only then the chromatophore of the old semi-cell divides, and one half of it passes into a new semi-cell. Thus, each individual of the closterium consists of two halves of different ages: one is older and the other is younger. The sexual process is the conjugation of two individuals immersed in a common mucus. The zygote is covered with a thick layered membrane and is well adapted to endure adverse conditions. All winter the zygotes are at rest, and for a long time the nuclei remain unfused. From the zygote, two young closteriums are formed, each receiving two haploid meiotic nuclei. One, small, soon degenerates. The second one becomes the nucleus of a new individual. The development cycle is monohaplobiont.

Objects: r. closterium.

Progress

1. Consider the closterium at m. and watch it move.

2. Examine the closterium cell at b. led away. and draw it. Designate the cell membrane, nucleus, chromatophores, pyrenoids, terminal vacuoles with gypsum crystals.

Questions and tasks

1. List the main types of morphological organization in green algae. Describe each type. Give examples.

2. What signs are typical for representatives of the green algae department?

3. What classes are the department of green algae divided into? What is the difference between representatives of each class?

4. What are colonies and coenobia in green algae? Give examples of colonial and coenobial green algae. What is the difference between colonial and multicellular organisms?

5. How does vegetative reproduction occur in green algae? Give examples.

6. How does asexual reproduction occur in green algae? Give examples.

7. What sexual processes are characteristic of green algae? Give examples.

8. Sketch schematically the life cycle of chlamydomonda, ulotrix, ulva, spirogyra. Sign on the diagram which generation is a sporophyte and which is a gametophyte, a set of chromosomes (haploid or diploid) for each generation and cells used for reproduction, the type of reduction division and the sexual process. Indicate the type of life cycle typical for these algae.

9. Fill in the table:

Comparative characteristics of classes and orders

10. Describe the role of green algae in the life of water bodies. Give examples of green algae that lead a terrestrial existence.

Department of Diatoms (Bacillariophyta, Diatomae)

An extensive department of unicellular and colonial organisms, uniting more than 10,000 species. Diatom cells are covered with a silica shell, consisting of two halves that fit on top of each other, like a lid on a box. The larger half is the epithecus and the smaller half is the hypotheca. Each half consists of a sash (bottom) and a girdle ring (girdle) soldered to it. Moreover, the belt of the epithecus is superimposed on the belt of the hypotheca. Under the shell is a pectin shell. Diatoms belong to the group of brown-colored algae, which are characterized by the presence of chlorophylls. a and With, masked by the yellow pigment fucoxanthin. The reserve product of carbohydrate nature is chrysolaminarin. Monadic cells are spermatozoa with one pinnate flagellum. Diatoms reproduce vegetatively, by longitudinal cell division with the completion of one valve - hypotheca. Sexual processes - conjugation and oogamy. After the sexual process, a zygote is formed that has the ability to grow (auxospore). Diatoms live in a diploid state and only their gametes are haploid.

Class Centric (Centrophyceae)

The Centric class combines algae with a radially symmetrical shell and the absence of a suture-nodular apparatus. All centric algae are immobile. The sexual process is oogamy.

Rod Melozira (Melosira)

Melozira is a filamentous colonial alga, consisting of the same type of cylindrical cells, interconnected by the contact of small spines located on the rounded surfaces of the valves. The shell of the melozira has wide belts, therefore, most often the algae is viewed from its lateral surface. The cells have several lobed chromatophores located along the wall, the center of the cell is occupied by a large vacuole with cell sap.

Melozira does not have a suture-nodal structure and therefore is immobile.

Reproduces by division and sexually. The sexual process is oogamy. In some cells, after reduction division, one egg is formed, in others - four spermatozoa with one flagellum. The zygote is covered with a thin, well extensible pectin membrane. Intensively growing zygotes are called auxospores. Since cells crushed after repeated divisions participate in the sexual process, the auxospore restores their original volume. Having reached a certain size, the auxospore develops its own shell. The developmental cycle of Melosyra is monodiplobiont.

Objects: r. melozira.

Progress

1. Examine the site of the Melosyra colony at b. led away. and sketch the algae from the side of the girdle and from the side of the sash. Label the colony cell, epithecus, hypotheca.

2. Locate and draw the auxospore.

Class Pennate (Pennatophyceae)

The Pennate class includes algae with bilateral shell symmetry, having a suture-nodular apparatus, and have the ability to move. The sexual process is conjugation.

Genus Pinnularia (Pinnularia)

The genus Pinnularia includes more than 150 species. It lives in fresh, lime-poor water bodies. Leads a benthic way of life at the bottom or in fouling of underwater objects. Pinnularia, like other diatoms, is of great importance as a food base for small animals and is the initial link in food chains in aquatic ecosystems. This is a unicellular algae with a suture-nodular structure and, as a result, is mobile. Among other unicellular diatoms, pinnularia is large and therefore convenient for study. From the girdle, the shell has a rectangular outline, and the valves are from linear to elliptical. The ends of the valves are mostly rounded, but may be attenuated and capitate. Nodules and two s-shaped slit-like openings (suture) extending from the peripheral nodules to the central one are clearly visible in the center and at the ends of the valve. Along the edges of the sash is clearly visible, especially on empty shells, a clear pattern of parallel partitions - sept, not reaching the seam. Pinnularia cells are mononuclear with two lamellar chromatophores, with curved edges. The wide flat side of the chromatophore faces the side of the girdle, and with its edges it goes to the side of the valve. Living active cells of Pinnularia are colored yellowish-brown, since fucoxanthin masks green pigments, but in dying cells, fucoxanthin is washed out, and the chromatophore becomes green. The cells have two vacuoles separated by a central cytoplasmic bridge. It contains the core. Pinnularia stores volutin, visible under a light microscope as dimly shining spherical bodies, and drops of oil. Under the shell, the cell is dressed in a mucilaginous pectin membrane. Pinnularia, which has a suture-nodular apparatus, actively moves, crawling along the substrate.

Pinnularia reproduces by division, running parallel to the valves. Each child valve receives one parent valve, while the second, completed valve, is always a hypotheca. As a result of this feature, at each division, one daughter cell is always somewhat smaller than the mother cell, and individuals of different sizes can be found in the population. The sexual process in Pinnularia was not found, auxospores are not formed. It can be assumed that large cells divide more often than small ones, and the smallest ones do not divide at all. The life cycle is monodiplobiont.

Object: r. pinnularia.

Progress

1. Consider pinnularia at b. led away. Sketch the cage from the side of the sash. Designate the cell membrane, suture, nodules, septa, chromatophore.

2. Sketch the cage from the side of the girdle. Label the epithecus and hypotheca.

Questions and tasks

1. What levels and types of morphological organization are typical for representatives of diatoms?

2. What are the structural features of diatom cells?

3. What is the structure of the shell of diatoms?

4. What are the principles of classification of diatoms?

5. What methods of reproduction are typical for diatoms?

6. How are sexual processes carried out in diatoms? What is an auxospore?

7. Where do diatoms live? What features of adaptation to the planktonic and benthic way of life do diatoms have? Give examples of planktonic and benthic diatoms.

8. Sketch schematically the life cycle of pinnularia and melosira. Sign on the diagram which generation is a sporophyte and which is a gametophyte, a set of chromosomes (haploid or diploid) for each generation and cells used for reproduction, the type of reduction division and the sexual process. Indicate the type of life cycle typical for these algae.

Department Brown algae (Phaeophyta)

The main pigments in brown algae are chlorophylls. a and With, carotenoids and xanthophylls, including fucoxanthin, which masks green pigments and gives algae a characteristic brown color. Spare products - laminarin (substance of carbohydrate nature); mannitol is a sugar alcohol and a small amount of fat. The pheoplasts are lamellar or more often numerous disc-shaped (granular chromatophore) located in the perinuclear space under the outer nuclear membrane that covers each pheoplast and forms the pheoplast endoplasmic reticulum. Pyrenoids protrude above the surface in the form of a kidney. The cells have one nucleus, large vacuoles with cell sap and small vacuoles containing tannins and called physodes.

The shell consists of two layers: the outer mucilaginous, containing alginic acid, and the inner, formed by a special kind of cellulose - alguose. Monadic cells with two heterocont and heteromorphic flagella are located on the lateral side of the cell. The anterior is long pinnate, covered with mastigonemes, the posterior is short and smooth. The range of morphological structures is large: from filamentous heterotrichous to differentiated lamellar tissue forms. In all brown algae, with the exception of representatives of the Fucus order, which lack asexual reproduction and are diplobionts, a change in generations is observed: in some it is isomorphic, in others it is heteromorphic. These different types of life cycle form the basis of the modern division of the brown algae into three classes.

With few exceptions, brown algae are marine algae, especially abundant in the cold waters of the northern and southern hemispheres.

Class Isogenerate (Isogeneratophyceae)

The class Isogenate includes algae with isomorphic alternation of generations or with heteromorphic, but with the dominance of the gametophyte.

Order Ectocarp (Ectocarpales) includes heterotrichous forms.

Genus Ectocarpus (Ectocarpus)

Ectocarpus is a widespread marine, benthic algae, found in all latitudes in the coastal strip of seas and oceans. Algae settles on rocks and other underwater objects, including plants. Being tolerant to different water salinity, ectocarpus participate in fouling of ships. The temperature range of ectocarpus habitats is also wide. It grows both in cold and warm seas, and is active in both summer and winter. Ectocarpus is a macroscopic (up to 60 cm) algae, filamentous heterotrichous, having the appearance of branched bushes.

At the base are horizontal creeping rhizoids that attach the algae to the substrate. The vertical branches at the base of the thallus, covered with a bark of rhizoidal filaments, become thinner towards the apex and end in long colorless cells. The increase is due to the division of cells located in different parts of the thallus. In the cells of the ectocarpus, there are small vacuoles with cell sap, one nucleus in the parietal layer of the cytoplasm, and several ribbon-like chromatophores with pyrenoids. In senescent cells, the chromatophore becomes disc-shaped.

Ectocarpus reproduction is asexual and sexual. Meiozoospores, kidney-shaped with two unequal flagella attached to the lateral surface, are formed in unicellular sporangia sitting on a unicellular stalk. Such sporangia are formed on diploid sporophyte plants. On haploid plants, multi-nested reproductive organs are laid. Each nest produces one reproductive cell of the monad organization. Most often, these cells behave like gametes and merge to form a zygote. They are morphologically the same type, but their behavior differs: physiologically, female gametes are less mobile and quickly settle to the bottom; physiologically male are more active. The zygote develops into a diploid sporophyte. The cycle described above corresponds to the diplo-haplobiont type with isomorphic alternation of generations, but the ectocarpus has deviations from this cycle, for example, gametes can germinate parthenogenetically without fertilization, giving new haploid individuals. Thus, apparently, the possible complete adaptation of the ectocarpus to the conditions of existence is achieved and its wide ecological amplitude is explained.

Objects: r. ectocarpus (herbarium specimens, micropreparations).

Progress

1. Consider the herbarium specimens of the ectocarpus. Sketch the appearance of the heterotrichous thallus of the ectocarpus.

2. Consider at b. led away. and draw from the preparation areas of the ectocarpus thallus with multi-chambered gametangia and single-chambered sporangia. Name the cells of the thallus, gametangia, sporangia.

Class Heterogenerate (Heterogeneratophyceae)

The heterogeneous class is characterized by a heteromorphic alternation of generations with sporophyte dominance and microscopic small gametophytes.

Includes algae with a complex thallus having a tissue structure. The growth is carried out due to the division of cells located at the point of transition of the leaf-shaped part of the thallus to the petiole (intercalary growth).

Genus Laminaria (Laminaria)

Two types of kelp are known and widespread in the northern seas: L. sugar (L. saccharina (L.) Lamour) and L. palmate (L. digitata (Hudz. Lam)), which form entire plantations in the upper sublittoral and are commercial algae . Laminaria is called "seaweed" and is a valuable food product used in animal feeding, as well as the manufacture of various food products and medicines for humans.

Laminaria is a large, complexly differentiated benthic attached algae, with a true tissue structure. Its meristematic cells are able to divide in three mutually perpendicular directions and form three-dimensional structures in which all cells are connected to each other by plasmodesmata. The thallus of the kelp is differentiated into three clearly distinguishable parts: powerful claw-like rhizoids with which it attaches to the substrate, a radially symmetrical part, the so-called petiole, and a flattened plate. The first two structures are perennial, while the lamina dies and grows again due to the intercalary meristem located in the upper part of the petiole. The internal organization of the kelp body is also quite complex. The petiole from the surface has densely closed cells containing grains of pheoplasts. In the deeper layers, the cells are colorless and elongated in the longitudinal direction. In the center of the cell are located loosely and form the core. The petiole gradually grows in thickness, and layers resembling growth rings are clearly visible on the transverse section. In the anatomical structure of the plate, the small cell cortex is also distinguished. In the center there is a "vein", the cells of which resemble in their structure the sieve cells of higher plants.

Laminaria reproduce sexually and asexually. Sporangia are located on the surface of the plate, forming whole spore-bearing areas or fields, on which sac-like sporangia and elongated sterile paraphyseal processes are located in a palisade layer. In sporangia, after reduction division, biflagellate reniform meiozoospores are formed, germinating into haploid organisms. The female and male gametophytes differ from the sporophyte. These are microscopic filamentous, underdeveloped plants (growths). They are short-lived, their main function is the production of gametes. The sexual process is oogamy. The zygote germinates without a dormant period and develops into a diploid sporophyte. Thus, almost all active life of kelp occurs in the diploid state. The development cycle is diplohaplobiont with heterotrophic alternation of generations, with sporophyte dominance.

End of introductory segment.

The ending. See No. 5, 6, 7, 8, 9/2002

Brown algae are also widely used in various industries. alginates- salts of alginic acid. The greatest application is found by water-soluble sodium alginate, capable of forming viscous solutions. It is widely used to stabilize various solutions and suspensions. Adding a small amount of sodium alginate to food products - canned food, ice cream - improves their quality. Alginates are also used in the production of plastics, synthetic fibres, coatings and weather-resistant building materials. They are used in the manufacture of high-quality lubricants for machines, absorbable surgical sutures, ointments and pastes in the pharmaceutical and perfume industries. In the foundry industry, alginates improve the quality of foundry earth; are used in the production of electrodes for electric welding, which make it possible to obtain higher quality welds.
Another important substance derived from brown algae is a six-hydric alcohol. mannitol. It is used in the pharmaceutical industry for the manufacture of tablets, the preparation of diabetic foods, the production of synthetic resins, paints, paper, explosives, and leather dressing.
The most famous and popular representatives of brown algae are kelp, or "seaweed". Genus kelp ( laminaria) has about 30 species distributed mainly in the Northern Hemisphere, especially in the Pacific Ocean. Perennial thalli of these algae reach a length of several meters and consist of an elongated oval plate, a stem and branched rhizoids, with the help of which the plant is attached to the ground. Laminaria usually grow at a depth of up to 20-30 m, in places with constant movement of water, attaching to stones and rocks.

Laminaria sugary (L. saccharina) is found here in the White, Barents, Kara and in all the seas of the Far East, and Japanese kelp (L. japonica), characterized in that a wide and thick median strip runs along the longitudinal axis of its plate, bounded at the edges by two longitudinal folds, in the northern half of the Sea of ​​Japan, as well as near the southern and southeastern coasts of Sakhalin and the South Kuril Islands.
Japanese kelp has excellent taste and is considered the most valuable commercial species among brown algae. It is used to prepare a variety of dishes, canned food and confectionery. In Japan and China, methods have been developed for the artificial cultivation of kelp, which makes it possible to collect stable crops from plantations. Due to the significant content of iodine and bromine, sea kale is also used for medicinal purposes - for thyroid diseases, sclerosis, nervous disorders, gastrointestinal diseases.
Brown algae of the genus fucus (Fucus) are also common in the cold and temperate seas of the Northern Hemisphere, where they often form large thickets in shallow water. Representatives of this genus are distinguished by a dichotomously branched thallus with flat branches that have a longitudinal rib and are attached to stones with a conical sole. Fucuses are used as fertilizers, as livestock feed, for the production of feed flour, alginates and other substances.

green algae

Green algae is the most extensive of all divisions of these plants, it includes about 15 thousand species. Representatives of green algae are distinguished primarily by the really pure green color of their thalli, which is caused by the predominance of chlorophyll in chloroplasts ( a and b) over other pigments (carotenoids). The reserve polysaccharide of green algae - starch - is deposited inside the chloroplast. Most green algae have a cellulose cell wall on top of the cytoplasmic membrane.
Most green algae are characterized by the predominance of the haploid phase in the life cycle - only the zygote has a double set of chromosomes, which meiotically divides with the formation of spores. However, among the representatives of the department there are both forms with a predominance of the diploid phase in the life cycle, and species with an isomorphic change of generations.
Most green algae live in fresh water, although marine species are also found.
Most often, the department of green algae is divided into three classes *. Class Representatives Isoflagellates characterized by asexual reproduction by zoospores with flagella of the same length and structure. Their sexual process is represented by isogamy, heterogamy and oogamy. The thalli of equiflagellates are diverse in shape, and the types of their morphological organization serve as important systematic features.
It is convenient to consider the features of this class of algae using the examples of a number of its representatives. Genus chlamydomonas(Chlamydomonas) includes over 500 species of unicellular algae, most of which live in fresh, shallow, well-heated and polluted water bodies: ponds, puddles, ditches, etc. With their mass reproduction, the water acquires a green color.

BUT- vegetative individual; B- palmeloid stage; AT- reproduction (young individuals inside the mother cell)

The chlamydomonas cell has a rounded or elliptical shape and is covered with a membrane, in old individuals the protoplast is somewhat lagging behind the back. The cell has one haploid nucleus, a cup-shaped chromatophore, in which the ocellus and contractile vacuoles located in the anterior part of the cell are immersed. At the anterior end there are also two flagella, which play the role of organs of movement.
When the reservoir dries up, chlamydomonas lose their flagella, the walls of their cells become slimy, and in this immobile state, the cells begin to divide. The walls of the resulting daughter cells are also mucilaginous, so that as a result a system of mucous wrappers nested into each other is formed, in which immobile cells are located in groups. This so-called palmelliform algal condition. When they enter the water, the cells again form flagella and pass to monadic(single) state.
Under favorable conditions, chlamydomonas intensively reproduces in a different way - the cell stops, and its protoplast, somewhat lagging behind the wall, sequentially divides longitudinally into two, four or eight parts. These daughter cells form flagella and come out in the form of zoospores, which, after a short growth, begin the same reproduction themselves. The sexual process in chlamydomonas is isogamy. Gametes are formed inside the mother cell, but in a larger number than zoospores - 32-64, and, accordingly, are smaller. After their fusion, a zygote is formed, in which reduction division occurs with the formation of haploid cells.
Along with the autotrophic way of feeding, chlamydomonas cells are able to absorb organic substances dissolved in water through the membrane, which contributes to the active purification of polluted waters in which these algae develop.

Representatives of the genus volvox(Volvox) are colonial organisms. These are the most highly organized representatives of the class. Their colonies have the appearance of mucous balls up to 2 mm in diameter, in the peripheral layer of which there are up to 50 thousand cells with flagella (similar to Chlamydomonas), fused with their mucilaginous side walls with each other and connected by plasmodesmata. The inner cavity of the ball is filled with liquid mucus. In such a colony, there is a specialization of cells: its peripheral part is made up of vegetative cells, and larger reproductive cells are scattered between them. About a dozen of them gonidia, cells of asexual reproduction. As a result of repeated divisions, they give rise to young, daughter colonies, which fall inside the parent ball and are released only after its destruction. The sexual process in Volvox is oogamy. Organs in which gametes, oogonia and antheridia are formed also arise from reproductive cells. In Volvox globular, oogonia and antheridia are formed from cells of the same colony (monoecious colonies), in Volvox aureus - from cells of different colonies (dioecious colonies). In the European part of Russia, both of these species are found in ponds and oxbow lakes, and during the period of intensive reproduction they cause "blooming" of water.

Chlorella (Chlorella) - unicellular algae about 15 microns in size - a widespread and well-known genus. Chlorella is very unpretentious and is found almost everywhere - in fresh waters, on damp earth, on tree bark, etc.
The spherical cell of chlorella contains one nucleus and a cup-shaped chromatophore. There is no ocellus and contractile vacuoles. The cell wall of some species of these algae, along with cellulose, contains sporopollenin- a substance extremely resistant to the action of various enzymes, also found in pollen grains and spores of higher plants. Chlorella reproduces exclusively by autospores (asexual reproduction), which are usually formed by 4–8 in one cell and are released after the rupture of its wall.
In the process of photosynthesis, chlorella is able to use up to 12% of light energy (land plants use only 1–2%), and the dry matter of its cells is very nutritious: it contains up to 50% of complete proteins, fatty oils, vitamins B, C, K. Chlorella is characterized very high breeding rates. Thanks to this, it has become an object of mass cultivation for use in a variety of ways.

Algae of the genus ulotrix(Ulothrix) live mainly in fresh water bodies, but can also settle on wet surfaces wetted by splashes of surf or waterfalls. One of the most widespread types is ulothrix girdled(Ulotrix zonata). Near Moscow, this algae is found in fast-flowing streams, and in the North-West region it often forms cotton-like growths on stones in the surf zone of large lakes.
The ulothrix thallus consists of unbranched filaments. All cells of the filament are identical (with the exception of the basal cell, which extends into a short rhizoid, with the help of which the filament is attached to the substrate at the beginning of growth) - their center is occupied by a vacuole, and the only belt-shaped chloroplast encloses the protoplast along the perimeter. The nucleus is one, located along the longitudinal axis of the cell.
During vegetative propagation, the ulotrix filaments break up into short segments, each of which develops into a new filament. Asexual reproduction of this alga is carried out by zoospores, which can be formed in all filament cells, except for the basal one. The sexual process of ulotrix is ​​isogamy. Most often, the transition to sexual reproduction is associated with the end of active growth and the onset of adverse conditions.

BUT- appearance of the thallus; B- cross section of the thallus

Thallus of seaweed of the genus ulva (Ulva) is a bright green two-layer plate with corrugated edges, about 10–12 cm in size, attached to the substrate with a base narrowed into a short petiole. Ulva cells are mononuclear with a parietal chromatophore and a large central vacuole. The most common method of vegetative propagation of Ulva is the germination of base cells with the formation of young plants. In contrast to the algae listed above, in the life cycle of which the haploid stage predominates, Ulva has an alternation of generations: a diploid sporophyte and a haploid gametophyte. The nuclei of sporophyte cells contain a double set of chromosomes, and during reduction division, haploid zoospores are formed. Germinating, they form haploid plants - gametophytes, capable of forming gametes. When the gametes merge, a zygote is formed containing a diploid nucleus and germinating into a sporophyte without a dormant period. Ulva is characterized by an isomorphic change of generations - its sporophyte and gametophyte look exactly the same in appearance.
Ulva is found in the seas of all climatic zones, although it prefers warm waters. For example, in the shallow waters of the Black Sea, this is one of the most widespread types of algae. Many Ulva species tolerate desalination; they are often found in river mouths.

Genus caulerpa (Caulerpa) includes about 60 species of algae, the creeping parts of the thallus stretching on the ground look like branching cylinders, reaching a length of several tens of centimeters. At certain intervals, abundantly branching rhizoids extend down from them, fixing the plant in the ground, and up - flat, leaf-like vertical shoots in which chloroplasts are concentrated.
Caulerpa thallus, despite its large size, does not have a cellular structure - it completely lacks transverse partitions, and formally it is one giant cell. This structure of the thallus is called siphon. Inside the thallus of the caulerpa is a central vacuole surrounded by a layer of cytoplasm containing numerous nuclei and chloroplasts. Various parts of the thallus grow at their tops, where the cytoplasm accumulates. The central cavity in all parts of the thallus is crossed by cylindrical skeletal cords - cellulose beams, which give the body of the algae mechanical strength.

BUT- appearance of the thallus; B– section of thallus with cellulose beams

Caulerpa easily reproduces vegetatively: when the older parts of the thallus die off, some sections of it with vertical shoots become independent plants.
Species of this genus live mainly in tropical seas, and only a few enter subtropical latitudes, for example, common in the Mediterranean Sea caulerpa sprouting(Caulerpa prolifera). Caulerpa prefers shallow waters with calm water, for example, lagoons protected from the action of constant surf by coral reefs, and settles both on various hard substrates - stones, reefs, rocks, and on sandy and silty ground.

Representatives of another class of green algae - conjugate - characterized by the absence of flagellated stages in the life cycle. They do not have asexual reproduction, and the sexual process is represented by a peculiar form - conjugation.

Conjugates, in particular, include representatives of the genus spirogyra (Spirogyra) - filamentous non-branching bright green algae, about 300 species of which are widely distributed in fresh water bodies around the globe.
Spirogyra thalli range in size from a few millimeters to ten centimeters and consist of a single row of identical cylindrical cells, each of which is capable of growth and division. In spirogyra, living in running water, rhizoids develop - cell outgrowths devoid of chloroplasts of various shapes and degrees of branching, with a thickened membrane. The inner layer of the cell wall of spirogyra consists of cellulose, the outer layer of pectin substances that form a layer of mucus, as if wrapping the entire thread and making spirogyra slippery and silky to the touch.
In the cell of these algae, ribbon-like spirally twisted green chloroplasts are clearly visible, located in the wall layer of the cytoplasm. The density of turns and the position of chloroplasts vary depending on environmental conditions: under unfavorable conditions, their growth lags behind cell growth, and the number of turns decreases sharply. The large nucleus of spirogyra with a clearly visible nucleolus is located in the center of the cell. It is surrounded by a layer of cytoplasm and, as it were, suspended on cytoplasmic strands extending from the parietal cytoplasm.
Vegetative propagation of spirogyra occurs when the thread is accidentally broken or broken into separate fragments under unfavorable conditions. The nuclei of spirogyra cells are haploid, a double set of chromosomes is present only in the zygote, which is formed by the fusion of protoplasts of vegetative cells of neighboring threads - conjugation. When the zygote germinates, a reduction division occurs.
Threads of spirogyra, intertwined and covered with common mucus, cover large areas of the bottom of rivers and streams.

Algae of the genus closterium (Closterium) are unicellular organisms. About a hundred species of this genus are known, living in ponds, sphagnum swamps, and small calm lakes. A crescent-shaped, with pointed ends, the closterium cell consists of two symmetrical halves - semi-cells. The cell wall also consists of two halves, soldered in the plane of symmetry. It has pores, especially large ones at the ends of the cell. Exuding through the pores at one end of the cell, the mucus lifts it; after that, the mucus begins to stand out at the other end. Thus, the closterium cell "tumbles", moving near the bottom.
Each semicell contains one large central chloroplast, consisting of an axial rod, from which several plates extend along the radii (so that the chloroplast has a stellate shape in a transverse section). In the plane of symmetry of the cell there is one large nucleus, and at the ends of the cell there is one vacuole with gypsum crystals.
The usual method of vegetative propagation of Closterium is cell division in the transverse plane. Daughter individuals receive one half-cell from the mother cell, and the missing one is completed anew. During the sexual process (conjugation), two closterium cells approach each other and dress in common mucus. In the region of symmetry, each conjugating cell forms processes that connect with each other - the conjugation channel. During the germination of the zygote, a reduction division occurs, and out of the four haploid nuclei formed, as a rule, two remain viable, forming two seedlings.

Representatives of the third class of green algae - Kharovyh , - are very different from the rest in that their filamentous multicellular thalli have a complex morphological organization. On the main shoots growing at the top (“stems”), at some distance from each other there are whorls of identical short lateral jointed shoots (“leaves”) with limited growth. The locations of the whorls are called nodes, and the sections of the thallus between them are called internodes.

In appearance, many of the charophytes are very reminiscent of horsetails, although this resemblance, of course, is purely external. Each internode on their thallus is one multinucleated, gigantic (up to several centimeters long), often covered with bark, cell incapable of division. And the nodes consist of several small mononuclear cells assembled into a disk, in the process of their division forming the lateral branches of the “stem” and the whorl of “leaves”. Shoots of characeae are attached to the bottom with the help of numerous thin rhizoids. These algae reach very large sizes - from 20–30 cm to 1–2 m.
Characeae do not have asexual reproduction, the sexual process is oogamy. Organs that produce gametes - multicellular oogonia and antheridia - are formed on the segments of the thallus, in the nodes. In the oogonium up to 1 mm in size, one egg develops, in the antheridium (its diameter is about 0.5 mm) - many male germ cells. In most species of characeae, oogonia and antheridia develop on the same plant, but there are also dioecious species.
About 300 species of charophytes are known. They are common in fresh water, especially with hard lime water, where they often form continuous thickets at the bottom. Some species are also found in sea bays.

Literature

Course of lower plants. - M .: Higher School, 1981.
Plant life. T.3. - M .: Education, 1977.
Garibova L.V. and etc. Algae, lichens and bryophytes of the USSR. – M.: Thought, 1978.
Raven P. et al. modern botany. – M.: Mir, 1990.
Chikov P.S. Medicinal plants are the way to health. - M., 1997.