Lub fulfills. The meaning of the word "lub" in the large Soviet encyclopedia. What was made from bast
Humanity has used wood for thousands of years. It was used for various purposes, mainly as a source of fuel. Wood is also an excellent building material; tools, weapons, furniture, containers, works of art, and paper are made from it.
Due to the presence of growth rings, which most tree species form in their trunks during growth, as well as as a result of seasonal fluctuations in temperature or humidity levels, scientists can fairly accurately determine the region in which the tree grew. Annual monitoring of changes in the width of tree rings and analysis of the content of certain isotopes of elements in them makes it possible to study in more detail the state of the climate and atmosphere in ancient times.
How is wood formed?
Wood is one of the components of the vascular-fibrous bundle; it is opposed to another important part of the bundle, formed from the same procambium or cambium - phloem or phloem. In the process of formation of vascular-fibrous bundles from procambium, two scenarios are possible:
- all procambial cells become elements of wood and bast with the formation of so-called closed bundles. This process is characteristic of higher spores, monocotyledons and some dicotyledonous plants.
- At the border between the wood and the bast, a layer of active tissue remains, which is called the cambium. In this case, open bunches are formed, which is typical for dicotyledonous and gymnosperm plants.
In the first scenario, the amount of wood does not change and the plant cannot thicken. If development follows the second path, then due to the work of the cambium, the volume of wood increases annually, and the plant trunk slowly becomes thicker. In tree species of the Russian region, the wood is closer to the center (axis) of the tree, and the bast is closer to the circumference (periphery). A number of other plants have slightly different mutual arrangement wood and bast.
It is the division of cambium cells in the stem that ensures its growth in thickness. During the process of cambial cell division? daughter cells formed are separated into wood, huh? - in the lub. For this reason, the growth is very noticeable in wood. The cambium is not divided evenly, this process depends on the season. In the spring and summer, division is active, as a result of which large cells are formed; by autumn, division slows down and small cells are formed. In winter, the cambium does not divide. This ensures an annual growth of wood, which is clearly visible in many trees, and is called the annual ring. By the number of growth rings, experts calculate the age of the shoot and the whole tree.
Wood contains already dead cellular elements with woody, mainly thick shells. The composition of bast, on the contrary, is represented by elements of living cells, with living protoplasm, cell sap and a thin non-lignified shell. At the same time, dead, thick-walled and woody elements may be found in the bast.
Both components of the vascular-fibrous bundle have another physiological difference. Raw sap, which is water with dissolved substances in it, moves along the wood from the ground to the leaves. useful substances. But plastic juice flows down through the phloem.
The process of lignification of cell membranes is characterized by the impregnation of the cellulose membrane with special substances, which are collectively called lignin. The presence of lignin and, at the same time, the lignification of the shell can be easily determined using certain reactions. Due to lignification, plant shells grow in thickness and harden. At the same time, with slight permeability to water, they lose their ability to absorb water and swell.
Bast structure
Phloem is the same as phloem. It is a conducting tissue of vascular plants. It is through it that the products of photosynthesis are transported to different parts of the plant, where they are used or accumulated.
In the stems of most plants, the woody bast is located outside the xylem, and in the leaves it faces the underside of the veins of the leaf blade. The vascular root bundles have alternating strands of phloem and xylem.
Based on its origin, tree bast is divided into:
- primary, differentiating from procambium
- secondary, differentiating from the cambium.
The main difference between primary and secondary phloem is the complete absence of medullary rays in the first. However, the cellular composition of both primary and secondary phloem is identical. They contain cells of different morphologies and perform different functions:
- sieve elements (cells, tubes and companion cells). These elements provide the main transport
- sclerenchyma elements (sclereids and fibers), responsible for the supporting function
- parenchymal elements (parenchyma cells) are responsible for short-range radial transport.
Sieve tubes live only a short time. Often their life span does not exceed 2-3 years, very rarely they live up to 10-15 years. Dead ones are regularly replaced by new ones. Sieve tubes take up little space in the bast and are most often connected in bundles. In addition to such bundles, the bast contains cells of mechanical tissue - bast fibers, as well as cells of the main tissue.
Lube functions
One of the main functions performed by young phloem is phloem transport of juice. This juice is a solution of carbohydrates (in woody plants it is mainly sucrose). Carbohydrates are products of photosynthesis, in fairly high concentrations - 0.2-0.7 mol/liter (about 7 to 25%). In addition to carbohydrates, juice also contains other assimilates and metabolites (amino acids and phytohormones) in much smaller quantities. The transport speed reaches tens of centimeters per hour, which is significantly higher than the diffusion speed.
Phloem sap moves from donor organs, in which the process of photosynthesis occurs, to acceptors - organs or areas in which these photosynthetic products are used or stored for later. Assimilates are consumed very intensively in the root system, shoot tips, growing leaves, and reproductive organs. Many plants have special storage organs - bulbs, tubers and rhizomes, which act as acceptors.
Linden bast is the inner layer of bark, which has a light yellow color. Its task is to ensure the strength of the stem. It is quite difficult to tear the bast layer across its width, but along the stem it easily breaks down into thin fibers of great length.
The bast part of the stem is often used on the farm; for example, linden bast is famous for making matting and washcloths from it.
Note that if the bark on a tree is cut in a circle down to the wood layer, then organic substances will no longer be transported to the roots, and the tree will die over time.
Bast (phloem) is a complex conductive tissue through which photosynthetic products (organic substances) are transported from leaves to all plant organs (rhizomes, fruits, seeds, etc.). Phloem is formed by the division of procambium (primary) and cambium (secondary) cells. The bast is located in the stem outside the cambium under the bark, and in the leaves - closer to the underside of the blade. Under the cambium in the trunk is wood.
Drawing. Tree trunk and its layers
Structure
Phloem tissue and its cellular composition are divided into three types depending on the functions performed: sieve tubes with cells; mechanical tissues (sclereids and fibers); bast parenchyma with parenchyma cells. Basically, bast consists of sieve tubes that allow dissolved nutrients to move down the stem. The tubes are formed by sieve cells that fit tightly and connect to each other.
Cells
The cells are living, thin-walled and elongated. They lack a nucleus, and the central part contains cytoplasm. The transverse walls of the cells have small through holes through which strands of cytoplasm pass into neighboring cells.
Sieve tubes extend along the entire length of the plant. In deciduous plants, satellite cells, which also take part in the transport of substances, adjoin and connect with the segments of the sieve tubes. Sieve tubes do not function for long, only one growing season; they gradually become clogged with callose and then die. Only some perennial plants have a lifespan of more than 2 years.
Functions
Mechanical fabrics - thick-walled bast fibers serve for strength and also perform a supporting function. Bast parenchyma contains thin-walled parenchyma cells, which serve for the deposition of reserve nutrients, as well as their short-range transportation.
If in the xylem the movement of dissolved minerals occurs only upward to the leaves from the roots, then in the phloem the movement organic matter(sucrose, carbohydrates, amino acids, phytohormones) from the leaves occurs to those plant organs that consume or store them. The highest intensity of substance consumption is observed in the tips of shoots, developing leaves, and roots. Many plants have storage organs: tubers, bulbs, etc. The transport speed is quite high and amounts to tens of centimeters per hour. Experiments have established that leaf donors most often feed nearby plant organs. For example, the leaves of the shoot provide fruits, the lower leaves provide roots. In addition, phloem transport is two-way, depending on the vegetative phase; for example, storage organs can transport carbohydrates to blossoming leaves.
If the bark on a tree is cut in a circle down to the wood, then organic substances will stop flowing to the roots, and the tree will dry out over time.
Related materials:
Phloem- a complex conductive tissue through which photosynthetic products are transported from leaves to places where they are used or stored (growth cones, underground organs, ripening fruits and seeds, etc.).
Primary phloem differentiates from procambium, secondary (bast) – derivative of cambium. Primary and secondary phloem, in addition to the different thickness of the sieve elements, it differs in that the primary one lacks core rays. Phloem. In typical cases, phloem consists, like xylem, of several histological elements. The main ones are the following: sieve tubes with companion cells, bast fibers and sclereids, bast parenchyma of various structures
Xylem– water and minerals dissolved in it move along the xylem from the root to the leaves.
Primary and secondary (wood) xylem contains the same types of cells. However, the primary xylem does not have medullary rays and this is why its organization differs from the secondary one. The xylem contains the following histological elements: trachea and tracheids, wood parenchyma, wood fibers.
Definition of shoot and its structure .
A shoot is a part of a stem with leaves and buds located on it and grown during one growing season. The main type of shoot of a green plant is aboveground, assimilative, bearing typical green leaves. But there may also be modified shoots that have changed the main function. We'll talk about this a little later.
The following parts can be distinguished on the shoot.
1.Stem with nodes and internodes. A node is the location on the stem where a leaf forms, and the distance between two nodes is called the internode. Metamorphoses of shoots are also stolons and tubers.
Tubers are thickenings of underground shoots like potatoes and Jerusalem artichokes. Tuberous thickenings begin to develop at the ends of the stolons. Stolons are short-lived and are usually destroyed during the growing season, which is why they differ from rhizomes.
The leaves on the tuber fall off very early, but leave scars in the form of so-called tuber eyes. Each eye contains 2-3 axillary buds, of which only one germinates. Under favorable conditions, the buds easily germinate, feeding on the reserve substances of the tuber and growing into an independent plant.
Thus, the third leading function of shoots is vegetative renewal and reproduction.
Some plant species produce very distinctive leaf tubers (e.g., thin-leaved core). These are modified leaf blades sitting on the petioles of rhizomes. These leafy tubers have lobes, pinnate veining, and even mesophyll tissue, but are achlorophyll-free and adapted for storing storage starch.
Anatomical differences between a typical stem and rhizome.
A rhizome is an elongated underground shoot. Its axial part is the stem. the anatomical structure of the rhizome has structural features characteristic of the stems of monocotyledonous and dicotyledonous plants. the function of this “stem” and its habitat are different, which is reflected in its anatomical structure.
Anatomy of the rhizome of monocots.
Like a typical stem, the rhizome of monocots has only a primary structure. On the outside, it is covered with suberized cells of the epidermis and one to three layers of also suberized cells of the primary cortex. Next is the storage parenchyma of the primary cortex. The inner layer of the primary cortex is endoderm. The primary bark of the rhizome is usually large in volume, sometimes equal to or larger than the central cylinder.
In the central cylinder, as in all monocot stems, many vascular bundles are diffusely located, however, many of them are concentric, especially the central ones, and the peripheral ones can be collateral, but all of them are closed.
Anatomy of the rhizome of dicotyledonous plants.
Internal structure The rhizomes of dicotyledonous plants can be of either bunched or non-bunched type. But in all cases, storage parenchyma is highly developed in the rhizome, and the integumentary tissue of dicotyledonous rhizomes is the periderm. The rhizome of bunch-type dicotyledonous plants will have the following tissues. Cover tissue – periderm; primary cortex with highly developed storage parenchyma (without collenchyma and endoderm); a central cylinder without sclerenchyma, with collateral more or less expanded secondary vascular bundles, with a core and wide medullary rays consisting of storage parenchyma. The rhizome of the non-bundle type is structured similarly, only, as in a typical stem, it has narrow medullary rays in the xylem and phloem parts
In the stem of the primary structure, as in the root, a central axial cylinder and a primary cortex are distinguished. But the ratio of these tissues is completely different: most of the cross-section is occupied by the central cylinder, which often has a large air cavity in the center. In addition, unlike the root, the primary cortex of the stem is covered with a typical epidermis with stomata. Mechanical tissues (collenchyma or sclerenchyma) often lie directly under the epidermis. These tissues are found in various combinations with parenchyma. Based on the nature of the arrangement of the conductive tissues, there are 1) fascicle-type stems (in which these tissues are laid in the form of separate bundles) and 2) non-bundle-type stems: in this case, the conductive tissues are arranged in a continuous ring.
the rhizome has poorly developed or completely absent mechanical tissues
but there is a large amount of storage parenchyma (connected with the storage function of the rhizome, unlike the stem
Section Horsetails. Taxonomy of the department. Habitat and distribution of individual representatives in Tatarstan, their role in nature and use in practice.
Equisetaceae are characterized by the presence of shoots consisting of clearly defined and regularly alternating nodes and internodes (segments), with whorled leaves. This morphological feature of horsetails sharply differed and differs from all higher plants.
Practical use horsetails.
Practical significance there are few horsetails. Many horsetails have been and are still used in folk medicine. Horsetail is included in the domestic state pharmacopoeia: summer vegetative shoots are used as a diuretic. Until the twentieth century, horsetails and horsetails were used to dye wool sulfur-yellow. The hard stems of wintering horsetail are widely used instead of sandpaper (for polishing) and for cleaning dishes. It should be noted that horsetails have a negative meaning. Among them there are many annoying, difficult to eradicate weeds (due to deep-lying rhizomes). Horsetails can cause poisoning in livestock (although information about their toxicity is controversial). different sources). Cases of animal poisoning are apparently associated with the presence of saponins and flavone glycosides in horsetails, the amount of which varies greatly depending on the habitat, time of year and other conditions. There is no information about the toxic properties of horsetails for humans. Young, slightly sweet, spore-bearing shoots of horsetail are even edible.
Characteristics of the meadow as a plant community
Meadow- , biogeocenosis, the plant component of which is made up of communities of perennial grasses. Most of the meadows arose on the site of cleared forests and bushes, drained swamps and lakes. Occupies an area of approx. 150-200 million hectares, in the temperate zone of the Northern Hemisphere (mainly in Europe). There are floodplain (flood) and continental (e.g. dry)
HELLEBORE- perennial meadow and forest grass of the lily family with a thick rhizome, large leaves and flower panicles
Meadow geranium
It has an astringent, analgesic, anti-inflammatory and analgesic effect, as well as the ability to dissolve salt deposits in urolithiasis and gout. Used as a hemostatic agent for uterine and nasal bleeding. Has antitumor effect
meadow clover belongs to the legume family (Fabaceae), it is a perennial herbaceous plant 15-40 cm high with
Infusions and decoctions of clover are used for edema of cardiac and renal origin, rheumatism, inflammation Bladder. Poultices with a decoction of the leaves are applied to tumors and wounds, and the fresh juice of the plant is used to treat allergic diseases.
Liliids (Liliidae). Herbs or secondary tree forms. Vessels only in the roots or in all vegetative organs. The perianth is well developed and consists of similar (usually petal-shaped) sepals and petals. The gynoecium is coenocarpous, rarely apocarpous. Ovules with double or, less commonly, simple integument. Seeds with abundant endosperm The subclass includes 4 orders.
Family Poaceae, or Poagrass, . There are about 10.5 - 11 thousand species in such plant communities as meadows, steppes, Po appearance cereals are easy to distinguish from all other plants. These are annual or perennial herbaceous plants with stems clearly divided into nodes and internodes; the nodes are usually slightly swollen, and the internodes are hollow inside (the stem is a straw). Corn and sugarcane, however, have a pith in their stalks. The leaves of cereals consist of a sheath that encloses the stem in the form of a tube, a leaf blade with parallel or arcuate venation. Branching of the stems of cereals occurs near the base, in the so-called tillering zone, consisting of closely adjacent nodes. Cereals are typically wind-pollinated plants. The perianth is simple, inconspicuous, stamens with flexible long filaments and swaying anthers attached to the filament in the middle; light dry pollen and feathery stigmas. Some cereals self-pollinate. O 2+2 T 3 P 1
A flower usually has one pistil, three stamens, two floral membranes and two lemmas (in wheat). The flowers are collected in an inflorescence - a simple spikelet (spikelet). The number of flowers in a spikelet ranges from one (in barley) to two (in rye) or more (in wheat). At the base of each spikelet there are usually 2 glumes. Simple inflorescences - spikelets - are collected into complex inflorescences such as a complex spike (rye, wheat, barley
panicle (oats, bluegrass), false ear, or sultan (timothy, foxtail), cob (corn) - inflorescence of pistillate flowers
The fruit of most cereals is a caryopsis. The largest part of the grain is the endosperm, which contains starch,
The Red Book includes beneken brome and four types of fescue.
***Ticket 19***
primary integumentary tissue, its functions and structural features.
Epidermis . This is the primary integumentary tissue, the border tissue, located on the leaves and on the green areas of the stems.
The epidermis arises from 1 layer of cells - dermatogen , it can be seen at the top of the stem.
Epidermis - as a tissue consists of two types of cells:
ü Basic cells of the epidermis
ü Closing cells of the stomata.
1) Basic cells The epidermis is small in height, large in area, closely adjacent to each other, has tortuous walls and thanks to this they provide a tight connection of cells:
a cell membrane – cellulose (secondary)
b cytoplasm – constant
c there is one large vacuole with cell sap. Juice can be colored with anticean
d is the core
e plastids – leukoplasts
The outer wall of the epidermis of the main cells can be impregnated cutin(fat-like substance). Sometimes the Cutin layer is large and indicates the presence of a cuticle. The cuticle can be smooth or folded. It helps the main cells protect the deeper cells from evaporation and sunlight.
Some epidermal cells have outgrowths - papillae, which also enhance the main function - to prevent other cells from drying out.
Structures, living or dead, can form on the main layer of the epidermis trichomes(hairs)
Dead trichomes are filled with air. They, like the papillae, enhance the functions of the main cells of the epidermis
The bast layer (or phloem) is the layer of wood immediately following the cork bark and preceding the cambium. In fact, the bast layer also refers to the bark of the tree. From a botanical point of view, wood is only the layers following the cambium inside the trunk. In a living tree, bast performs a transport function for nutrients, this is the main function.
We are interested in the importance of the bast layer for the construction of log houses. Should I remove bast when processing logs or not?
If we are talking about mechanized processing methods, then the question of preserving the bast layer does not arise, since in the manufacture of rounded logs, for example, even the sapwood, the layer next to the cambium, is damaged. In practice, it is impossible to preserve bast when processing with a planer (planed log).
Among the owners of log houses, developers, builders, craftsmen and experts in specialized construction publications, there are many both opponents and supporters of preserving bast. Opinions are divided approximately equally.
We also note that no one recommends preserving the cambium (if the bast is removed). Because the cambium is a rich breeding ground for insect pests and for the development of fungus and mold. In theory, bast is also a nutrient medium, since it contains nutritious tree sap.
On the other hand, this is while the tree is alive and growing. In a log, nutritional juices no longer pass through the bast. At the same time, the bast layer protects the wood from the penetration of moisture and steam. That is, it has some waterproofing (or, rather, restraining) properties. And this is good for a freshly cut log!
By protecting the wood from getting wet, bast also protects it from rot and mold. And being a vapor barrier with limited vapor permeability, the bast layer prevents the upper layers of the log from drying out too quickly. This is good, because the log will dry more evenly, which means its shrinkage will also take place more evenly throughout its entire thickness. As a result, the degree of warping and cracking of the log will be reduced.
By the way, experts who support the preservation of bast indicate that logs with bast are less susceptible to cracking and fungal attack:
Hardening of the dried bast and the formation of a crust will protect the log from insect pests.
Opponents of preserving the bast layer point out, however, that on the end cut of a log from which the bast has not been removed, traces of fungal damage are often found along the edge.
But if you look more closely, you can see that:
- firstly, the cambium and sapwood are affected (there is no way to remove the sapwood, because it is the majority of the log!);
- secondly, fungal damage to wood occurs at the cut - where the integrity of the layers is broken, and the bast layer does not protect the wood in any way.
In general, the issue of removing bast is not critical. One way or another, logs are treated with bioprotective agents, especially, as follows from the reasoning above, it is worth protecting the ends. Whether or not to leave the bast layer depends more on the aesthetic expectations for the appearance of the log house. The brownish rough texture of the log with a bast layer will give the log house a wilder, more brutal look. Some people like it, some don't.
Wood sawn in different directions has a different texture (see picture) and differs in its qualities and properties.
In a cross-section of a woody plant trunk, the following basic macrostructural units of wood can be distinguished:
- Cambium
- Sapwood wood
- Core
Bark- a protective covering of a tree trunk, consisting of an outer cork and an inner splint layer. This is a kind of tree skin that protects it from the effects of the external environment, and also participates in the regulation of respiration.
Lub- the inner layer of bark (phloem) immediately adjacent to the cambium, consisting mainly of living cells, performing the conducting function of the tree crown to its root system.
Cambium- a single-cell layer of living cells, alternately dividing towards the sapwood and towards the bast, ensuring the growth of the tree in thickness.
In a cross-section of wood, concentric layers of growth can be distinguished, called tree rings, which are lighter towards the surface of the tree and darker at the center. The light part of the wood is called sapwood, and the dark part is called heartwood.
Annual ring- a layer of wood formed in one year.
On a radical section, the annual layers have the appearance of longitudinal and straight stripes, on a tangential section - winding cone-shaped lines. By counting the growth rings, you can find out how many years a tree has lived.
Sapwood- like, the younger part of the trunk is less resistant to decay than the core, but more elastic. The width of sapwood varies depending on the species, growing conditions and other factors. In some species, the core is formed in the third year (yew, white acacia), in others - in the 30...35th year (pine). Therefore, the sapwood of yew is narrow, and that of pine is wide.
Core is formed due to the death of living wood cells, blockage of water supply pathways, deposition of tannins, dyes, resins, salts, therefore, the core is usually much darker than the sapwood. As a result, the color of the wood, its mass and characteristics change. mechanical properties.. The core of many species is painted in a darker color; it is the most valuable, strongest part of the wood.
Heart-shaped rays. On a cross section of some rocks, light, often shiny, lines directed from the core to the bark - heart-shaped rays - are clearly visible to the naked eye. Heart-shaped rays are present in all breeds, but are visible only in some. The medullary rays are especially visible in oak, beech, and sycamore. The medullary rays serve to pass water, air and organic substances produced by the tree in the transverse direction along the trunk.
The core is located inside the first annual layer, in the center of the trunk. The core is located in the center of the trunk and runs along its entire length. It is a loose tissue that is easily destroyed by living organisms, consists mainly of living cells, formed due to the division of cells of the apical educational tissue as the tree grows in height. The core is not used in construction.
Coniferous trees are characterized by the presence of resin ducts, in which extractive, tannin, and essential substances accumulate, giving coniferous wood a unique aroma.
Forest wood is usually light-colored. Moreover, in some species the entire mass of wood is painted in one color (alder, birch, hornbeam), while in others the central part has a darker color (oak, larch, pine). The dark part of the trunk is the core, and the light peripheral part is the sapwood. Some coreless rocks exhibit darkening of the central part of the trunk. In this case, the dark central zone is called the false nucleus.
Depending on the relative moisture content and the ratio of the size of sapwood and heartwood, tree species are divided into heartwood and sapwood.
In heartwood, the sapwood has a significant moisture content and is lighter in color than the heartwood. Soundwood species have wood that is uniform in color. The moisture content in the kernel is less than in the sapwood. Sapwood species are distinguished by the most uniform structure; the core and sapwood are practically indistinguishable either in color or moisture content.
The pattern that layers, vessels and core rays form on the surface of wood parts is called wood texture. Wood species such as walnut, oak, ash, Karelian birch, mahogany and others have a very beautiful texture, which they try to preserve and make clearer during finishing.
