Internal structure of the stem. Cork tree: description

When it comes to natural sustainable building materials, one of the first materials that comes to mind is cork. Today it is used in various fields and for various purposes. Technical cork is used for heat and sound insulation of rooms, as well as a substrate for many floor coverings, such as laminate. What are the features of this material, why it is so popular - we will tell in this article, as well as dwell on the technical characteristics and methods of using technical cork.

Features of cork materials and their advantages

Why are cork materials considered environmentally friendly? The fact is that the raw material for their production is the bark of a tree - cork oak. And in the production of final materials no synthetic substances are used, the material is obtained exclusively natural.

Cork oaks grow in the Mediterranean countries, of which Portugal is considered the largest supplier of cork materials. When the age of the cork oak reaches 25 years, the bark is removed from it for the first time. Due to natural intensive regeneration, the bark grows again and the tree does not die. After 9 years, you can again remove the bark from the tree, and with each removal the quality of the bark becomes better and better.

After removal, the bark is dried in natural conditions, and then sent to a factory where various products are produced. For the production of technical cork, the bark is crushed, and then the crushed bark granules are pressed under pressure and treated with steam. At the same time, additional binders are not used, as is the case with artificial polymers, since the composition of the cork itself includes suberin, a natural glue, which is more than 45% in the material. The technology for the production of cork materials is called agglomeration, which is why the positions of technical cork are called black cork agglomerate and white cork agglomerate. They differ from each other only in that the bark of the tree branches is used for the white agglomerate, and the bark of the trunk is used for the black agglomerate.

The unique feature of cork is its honeycomb structure. For every 1 cm3 of cork, there are up to 40 million honeycomb cells. Each cell has the shape of a polyhedron with 14 faces, the interior of the polyhedron is filled with a gaseous mixture. It is thanks to this peculiar structure that cork materials have excellent thermal insulation properties, and also do not allow water and gaseous substances to pass through. The cells are separated from each other by intercellular partitions.

Cork materials have both purely technical advantages over the rest, and have other advantages that can play a decisive role when choosing an insulating material.

Advantages of technical cork:

• Full environmental friendliness and hypoallergenicity. No harmful substances are emitted from cork materials, either at rest, or when heated or burned.
• Cork easily restores its shape after compression or torsion, bending. The material is exceptionally resilient. Even after years of use, it does not slip and does not get trampled, but continues to pleasantly spring underfoot.
• Cork is a natural antiseptic, so building materials from it are not subject to decay and the appearance of mold fungi.
• Cork is not eaten by rodents and insects.
• Cork materials are not afraid of ultraviolet radiation and do not let it through.
• Do not electrify, do not accumulate static electricity.
• Cork materials do not emit phenols, chlorine and cyanides or other hazardous substances when burned. So that the cork does not burn, it is treated with a special substance, after which it can be attributed to class G1 (non-combustible substances).
• Due to its natural unique structure, cork has a low thermal conductivity, which allows it to be used for insulation or thermal insulation of buildings.
• Also, the cork has excellent soundproofing properties, reducing the noise coming from the street.
• The material is comfortable to use, durable and versatile.
• Safe for the environment, as it is disposed of naturally.
• Technical cork retains all its properties at low temperatures, therefore it is used in the production of refrigerating chambers.
• The water resistance of the cork allows you not to worry about the material even in case of flooding at home.
• As exceptional features, the following can be distinguished: the cork reduces the level of radioactive radiation, and also isolates from the harmful effects of technopathogenic zones.

Also, cork materials are not afraid of alkalis and other substances.

Depending on the purpose for which it will be used, technical cork can be bought in two forms: in rolls or in sheets. They differ not only in the form of release, but also in the thickness of the material. Let us consider in more detail the characteristics and features of the use of rolled and sheet technical corks.

Technical roll cork is also called a cork substrate. It is usually produced in rolls with a width of 1000 and 1400 mm, but the thickness of the material is of greater importance. The thickness of cork in rolls can be 2 mm, 2.5 mm, 3 mm, 4 mm, 8 mm, 10 mm.

From the table above, you can get information about the technical characteristics of the rolled and sheet positions of the technical cork.

It can be added to the above that the service life of the roll substrate is equal to the life of the building, it is one of the most durable natural materials.

Humidity material maximum 7%, which is extremely important during installation and further operation.

Permanent deformation 0.2%. Due to such low rates, the cork material does not wrinkle and returns to its original shape after prolonged loads. For example, already 1.5 minutes after the cessation of exposure, the residual deformation is only 0.35%, after 15 minutes - already 0.25%, and after 150 minutes - only 0.17%.

The roll stopper is inert in relation to various chemicals.

pay attention to sound insulation coefficient. With a cork thickness of 2 mm, it is 16 dB, and with a larger thickness (4 - 10 mm), the sound absorption coefficient can increase to 22 dB or more.

Also important sonic shock resistance- 12 dB.

Deformation modulus of elasticity 2000 - 2500 kgf/cm2. This suggests that the material is able to withstand enormous loads without significant deformation and is not subject to destruction. Thanks to these properties, it can be used on many construction sites where the pressure of heavy equipment, for example, is very high.

Rolled technical cork is used as a heat-insulating and sound-proofing material. Fits under laminate, linoleum, parquet board and panel parquet, acting as a substrate that reduces the transmission of popping sounds from movement on a wooden floor. Also, the substrate serves as a heater between the base under the floor covering and the floor covering itself.

When equipping underfloor heating, a roll cork is also used and performs all the same functions.

An important advantage of using rolled cork for arranging floors is that the material allows you to level out small irregularities in the base, and also has excellent shock-absorbing properties.

Also, a roll cork can be used for insulation and soundproofing walls and ceilings, but this is less convenient than using a sheet technical cork. The fact is that the roll cork must be straightened to fix it on the surface, and the sheets are already even. As a substrate on the floor, roll cork is ideal, as it is pressed down by the floor covering. When insulating walls and ceilings, this is inconvenient.

When laying a rolled technical cork on the floor, the temperature in the room should not be lower than +10 °C, the humidity should not be higher than 75%. Laying can begin a day after the roll is unpacked and the material is straightened. The floor screed must be level, clean and dry, the residual moisture must not exceed 2.5%. During installation, the roll is cut into the required segments, which are laid on the floor surface without gaps. The joints are carefully glued. By the way, you can not fix the roll underlay to the floor mechanically, only glue it.

Technical cork in the form of sheets differs from rolled cork only in the strength of the material and dimensions. Usually it is a plate 940x640 mm with a thickness of 2 to 10 mm. The most common positions are cork sheets with a thickness of 4, 6 and 10 mm. For sheet technical cork, the price depends on the thickness of the material, because it also affects the technical properties.

In the table of characteristics of cork sheet, it is clearly seen that the so-called white agglomerate has a large sound absorption, which means it is more suitable for soundproofing rooms.

In addition, I would like to note that the material is easily restored after pressure is applied. For example, when a load of 7 kg / cm2 is applied, the compression is 10%, and after an hour it is already 0.7%.

Sound absorption coefficient leaf cork, measured at a frequency of 2.1 kHz, is 0.85. This allows you to significantly reduce noise, as well as completely eliminate reverberation. This is especially important when soundproofing recording studios and cinemas. After all, reverberation is the propagation of the sound of a reflected sound - an echo.

Application of technical sheet cork

Sheet technical cork is used for thermal insulation and soundproofing of premises. It isolates the floor, walls, floors, ceiling. In the room, which is insulated with a technical cork, there is no echo and minimal noise from the street.

Technical cork can be found in any environment, so it can be used both in the decoration of the external facade, and in the interior decoration of the room, and as a substrate for flooring and the "warm floor" system, as well as a rolled cork. As a heater, technical cork can be used in ceilings, and on the floor, and on walls, and on the roof, and on external walls.

Important! The only restriction on the use of technical cork is the production facilities where metal is processed. The fact is that metal shavings quickly clog the pores of the cork, and it ceases to perform its functions.

In combination with other materials, technical cork significantly reduces noise and reverberation. Cork is also used to reduce vibrations coming from machine tools and other mechanisms, no matter what load they put on the cork.

Cork provides the best sound absorption in the high frequency range above 1.5 kHz. This makes it possible to completely isolate the room from sharp loud sounds coming from the street, such as barking dogs or screaming. Also, when soundproofing partitions between rooms, you can isolate the room so that you will not hear the stereo system or TV.

But to reduce the vibration noise that is transmitted through the floors, or the vibration of mechanisms, the cork is not capable. Actually, like any soundproofing.

For the best sound insulation, the room is finished with cork in a complex: ceiling + walls + floor. To improve the acoustic properties of the cork, it is desirable not to cover it with another finishing material. It is possible, for example, to use cork decorative panels in addition to technical cork.

The technology of mounting a sheet technical plug is practically the same as mounting a rolled substrate. The only difference is that the sheet material can be laid immediately, as it is already even. Sheets are glued to the surface with special glue, always end-to-end. Sometimes sheets are fixed mechanically, but much less often.

And finally, the advantages of a sheet cork over a roll cork, which were noticed by professional installers:

• The leaf cork is denser.
• It is easier to install, since one person can handle it, unlike a rolled one, where an assistant is required.
• The sheet cork does not need to be leveled.
• Easier to cut to desired size.
• The sheet cork does not break and crack, as it is not rolled up.

Technical cork is a versatile material that is used in almost all places where insulation is needed: both indoors and outdoors. An indisputable plus is water resistance and resistance to the influence of mold, rodents, insects. The only drawback of technical cork is the high price compared to synthetic insulating materials of the same class.

The following main functions of plant stems can be named:

movement of water and dissolved minerals from roots to leaves;

movement of organic matter from leaves to all other organs of the plant (roots, flowers, fruits, buds and shoots);

removal of leaves to sunlight and support function.

In connection with the functions performed, the stems of higher plants, especially angiosperms, acquired their characteristic internal structure.

As you know, plants stems are woody and herbaceous. According to the internal structure, they differ from each other in the stronger development of some tissues and the underdevelopment of others. The clearest picture of the internal structure of the stem can be seen on the cross section of the tree.

The stem of a woody plant usually consists of four layers: bark, cambium, wood and heartwood. Moreover, each layer can include cells of different tissues. So the composition of the bark includes peel, cork, bast fibers, sieve tubes and other tissues.

In young stems of woody plants, skin. Like the skin of leaves, it has stomata through which gas exchange occurs. Under the skin or, if it is not, on the surface is cork. In a number of trees, the cork forms a fairly thick layer. The gas exchange tube contains lentils, which are tubercles with holes. Cells of the peel and cork belong to the integumentary tissue. They protect the internal parts of the stem from damage, penetration of pathogens, and drying.

Under the cork there may be a so-called primary cortex, and already under it is bast, which consists mainly of sieve tubes and bast fibers. Sieve tubes are bundles of living cells. They move organic substances that were synthesized in the leaves during photosynthesis. Cells of bast fibers have thick walls. Bast fibers are strong enough, they perform a mechanical support function.

Under the bark is a thin layer cambium, which is an educational fabric. Its small cells actively divide during the growing season of the tree (from spring to autumn) and provide thickening of the stem. The resulting cambial cells, which are closer to the cortex, differentiate into bast cells. Those cambial cells that are closer to the wood become wood. More wood cells are formed over the summer than bast cells. On a tree saw cut, the wood cells of each year are separated from each other by darker small autumn wood cells. Thus, growth rings are visible.

Below the cambium is wood, which usually makes up the bulk of the stem of a woody plant. In the wood are vessels. An aqueous solution moves along them from the roots. The vascular cells are dead. In addition to vessels, there are other types of tissues in wood. So there are cells with thickened strong walls.

core usually consists of loose storage tissue, consisting of large cells with thin walls.

In our modern times, construction keeps pace with the times. There are many kinds of finishing materials in the world. Today we will talk about a tree that gives us such a wonderful material as cork. It has been used by people since ancient times, not only in construction, but also in industry. The bark, which after proper processing turns into a cork, is formed in many plants.

In large quantities, sufficient for industrial use, it can be obtained from only three trees: the Amur cork tree (Amur velvet), Chinese variegated oak and cork oak. Cork is the top layer of the bark with deep cracks. Thanks to its dead cells, impregnated with suberin, it does not allow water or gas to pass through. It is worth getting to know the cork oak, which gives such a desired product.

Cork tree: description

From this plant it exudes strength, because oak has been considered a symbol of power and greatness since ancient times. The cork tree grows up to 20 meters in height. The crown is in the form of a tent with powerful branches. In plantations, this plant acquires a cylindrical shape.

The bark on thick branches and trunk is covered with an impressive cork layer. The cork leaf is oval or elliptical, 4-7 cm long and 1.5-3.6 cm wide. Leaves can be with small sharp teeth or entire. The top is shiny green, the bottom is gray densely pubescent. Leaves live 2 years, then fall off.

Acorns ripen on a short fruiting 2-3 pieces. In the first year of a tree's life, it is already possible to harvest acorns. Their size is about 3 cm in length and 1.5 cm in diameter. The plush is gray-pubescent and is 1/2-1/3 the size of the fruit.

cork bark

Cork oak is capable of regenerating bark layers. Cork formation is very slow, in one year it grows to approximately 7-8 mm of valuable layer.

An oak with such an unusual bark grows in areas with extremely hot and dry climates. By rewarding this plant with a cork layer, nature made sure that it was protected from overheating and drying out. Everyone knows how hot and merciless the subtropical sun can be.

Cork oak bark has small pores that contain air, so it is considered a wonderful insulator and protective layer of the plant.

Where is cork oak found in nature?

The cork tree grows in the wild in the coastal belt of Portugal. This country is rightfully considered the leader in cork production. It is here that the greatest variety of products from this raw material is observed. You can buy anything: a bag, wallet, shoes, souvenirs... It is also known that in 2010 a bride ordered a wedding dress made of cork, in which she walked down the aisle.

Amazing oak plantations are located in Italy, Spain, Morocco, France, Algeria and Tunisia. These plantations occupy an area of ​​about 2-2.5 million hectares. Every year, the owners of cork plantations harvest 300-360 thousand tons of cork.

The process of harvesting the bark

Harvesting bark is a very complex and time-consuming process. Collectors must climb ladders to a great height in order to find a layer of at least 3 cm. Having found the right place on the tree, the worker makes a cross cut of the cork around the circumference of the trunk, and the same is done below. Then the top and bottom are connected with one cut going from above, a wooden device is inserted between the dead bark and the bast, and the cork layer is very carefully separated.

The collected raw materials are stacked in special rooms for drying, where they are stored for several weeks, awaiting the next stage of processing.

On industrial plantations, the first crop of bark is harvested from fifteen-year-old trees. The best raw cork can be obtained from oak aged 30 to 150 years. Only after the third harvest is the bark of the highest quality.

The process of removing the bark is traditionally considered manual, this occupation was practiced a thousand years ago. The cork tree does not suffer from such processing if everything is done carefully and correctly. The bark grows back over time and becomes smoother every year, which increases its value. Harvested once every ten years. If we take into account the fact that this plant can live up to 200 years and even longer, then cork is collected about twenty times during its life.

Industrial use

As mentioned earlier, cork bark has been successfully used by mankind since ancient times. The peoples of the Mediterranean made shoes from cork and used it in the manufacture of gear. Our ancestors also clogged vessels with wine, water, vinegar and oil with it. The chroniclers of Ancient Rome in their descriptions talk about the use of cork bark in the construction of prefabricated housing as an excellent heat insulator. Such material was especially appreciated in field conditions.

In the modern world, cork raw materials have become even more popular. Cork is valued as an interesting finishing and building material. Wallpaper, linoleum, parquet, panels are made from it... Light and strong soles, rescue water tools, souvenirs are also made from this amazing bark... Cork is of considerable importance for winemakers. After all, only through such a high-quality blockage can wine breathe for many years.

Fellems. First, a layer of phelloderm cells is formed, which forms a layer of phellogen cells. Phelogen cells are divided into two parts: upper and lower. The upper cell (fellema) immediately dies and is covered with a thick layer of suberin (a substance that does not allow water and gases to pass through). The lower cell continues to divide, forming a phellem. In some plants (for example, pine, tulip tree, euonymus), the cork consists of thin-walled corked cells and phalloids - cell layers with lignified, but not corky walls.

The cork performs the following functions:

• protection against mechanical damage,
• protection against the penetration of pathogens,
• dry protection,
• mechanical support due to the rigidity of the phellem cells.

see also

Notes

Literature

• Biological Encyclopedic Dictionary / Ch. ed. M. S. Gilyarov; Editorial: A. A. Baev, G. G. Vinberg, G. A. Zavarzin and others. - 2nd ed., corrected. - M .: Soviet Encyclopedia, 1989. - S. 506. - 864 with. - 150,600 copies. - ISBN 5-85270-002-9

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- (caulis), the axial part of the shoot of plants, consisting of nodes and internodes. It grows in length due to the apical (in the cone of growth) and intercalary, or intercalary, meristems. Carries leaves, buds and sporulation organs, in angiosperms ... ... Biological encyclopedic dictionary

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Higher plants are divided into herbal and woody, respectively, two types of stem structure are distinguished. A distinctive feature of woody plants is the constant growth in thickness, which stops only when the organism dies. Herbaceous plants are limited in growth due to the characteristics of the life cycle. There are no significant differences in the structure of plant stems.

Stem- this is the axis of the shoot, with leaves and buds located on it. The structure of the stem can be primary - during the formation of a new plant, when the cells are not yet differentiated (in monocots it remains for life). For dicots and gymnosperms, a rapid change in the primary stem is characteristic, as a result, a secondary structure of the stem is formed (due to the action of the cambium and fellogen).

Stem

What is the stem made of?

The structure of the stem of a woody plant includes 5 departments:

• Cork;
• cambium;
• wood;
• core.

Cork

In only germinated plants, the outer layer is represented by a skin, which, after a certain time, is replaced by a cork. The peel protects the stem from moisture evaporation and the action of harmful microorganisms that lead to plant diseases.

On the surface are stomata required for efficient gas exchange. Direct absorption of oxygen is carried out thanks to lenticels - small tubercles on the bark, equipped with a hole. Formed from cells with a large intercellular space. Under the skin are green cells (they contain chloroplasts). After formation, the corks turn white and are already referred to as bast.

The functions of the cells of the outer cover of the stem: photosynthetic, protective, gas exchange.

Lub

Lub is divided into soft(includes conduction system and parenchymal structures) and solid. The color is whitish, there are such structural units of the bast: sieve tubes, bast fibers, cells of the main tissue.

sieve tubes- This is a collection of cells that have many holes on the surface through which organic substances flow.

Bast fibers- This is a mechanical tissue, has elongated cells, with a dense wall. Gives plants flexibility and strength.

Cambium

Between the outer and inner ball of cells is the educational vascular tissue - cambium. The precambium of the plant's primary structure serves as the basis for tissue formation.

The cambium cells are elongated, the cytoplasm is green, and the nucleus is fusiform. On the cut, you can see a circular layer of educational tissue, but true cambial cells form a single-layer ball, because after division, only one cell retains the properties of the original one.

Wood

Wood is the main component of the stem. Dense, wide, cells of different types and sizes are visible in its composition. The following parts are distinguished: vascular tissue, tracheids, wood fibers.

Vessels formed from connected tubular cells placed on top of each other, the walls between them partially dissolved, so the liquid can move freely. The main functions of the stem vessels are the movement of dissolved salts, nutrients from the root to the leaves, new shoots.

Tracheids are a system of dead cells with intercellular pores through which fluid flows. The speed of movement of solutes is lower than in conductive tissues.

Wood fibers consist of parenchymal cells that accumulate nutrients and thick-walled cells that perform a supporting function.

Core

Core- located in the center of the trunk, formed from large living and dead cells. Living tissue contains tannins. Small cells located near wood accumulate sugars and starch.

What is the function of the core of the stem?

The main function of the core of the stem is the storage of nutrients necessary for plant growth. The core contains essential oils (beech), resins, tannins (tea bush). In some plants (in rhizomes, tubers), core cells retain the function of the meristem (educational tissue capable of dividing all its life).

What are the functions of the stem

1. support- the stem is the core of the plant, provides its support; a place for the growth of leaves, flowers;
2. conductive– transport of dissolved substances from the root system to leaves and branches, new shoots;
3. storage- ensures the constant presence of water and nutrients inside the stem;
4. protective- protects against the action of dangerous agents, eating by animals (thorns, thorns develop);
5. vegetative propagation- for individual plants (citrus, pineapple) the only way to get offspring;
6. photosynthesis- the presence of chloroplasts in green cells makes it possible to participate in the processes of energy conversion;
7. assimilation of organic matter, an example of cacti, in which the stem takes on the function of leaves;
8. axial (mechanical)- brings the plant to the sun (leaves - for photosynthesis, flowers - for pollination).

stem growth

The growth of the stem in thickness occurs due to the presence of educational tissue (cambia).

Favorable conditions for stem thickening are the presence of heat and sufficient moisture; in winter, cell reproduction does not occur. The thickness of cadmium does not change during division, since only one of the two newly formed cells remains in the structure of the educational tissue, while the other passes to wood or bast. The number of cells moved to the central part of the stem exceeds the number of cells inherited by the bast by four times.

growth rings, which are visible on the transverse section of the stem, are formed due to the different shape of the cells formed in the spring and autumn. After spring awakening, cadmium begins to actively divide, forming large cells with thin walls. With the onset of summer, and especially autumn, the cells become smaller. In winter, the division of the educational tissue does not occur, and in the spring the process of reproduction of large cells is turned on again. Such cellular alternation can be easily traced in tree sections. Thus, their age is calculated.

Tree rings are used to judge the weather in a particular year.. If the ring is wide, then the tree received a lot of moisture and solar heat, if it is narrow, then there was little rain in the spring-autumn period. Also, on the south side, a wider part of the ring is observed, because the tree received more heat here.

The growth of the stem in height is carried out with the help of the meristem of the growth cone (apical bud). The cells of the lower part of the cone give rise to the formation of leaves. After that, the cells begin their growth, stopping division. The increase in cell size is due to the growth of vacuoles.

If the stem is broken or artificially deprived of the apical bud, growth in height stops, lateral shoots begin to develop.

The parts of the stem where leaves develop are called nodes. Several leaves can grow from one node, this determines their location.

Another- one leaf sprouts from one node, they are placed spirally on the stem, do not prevent sunlight from entering the underlying leaves (birch).

Opposite- two leaves are in the same node, opposite to each other (mint).

Whorled- one node has three or more leaves, this arrangement is quite rare (crow's eye).

Types of arrangement of buds on the stem

apical- the kidney is at the top of the shoot.

Lateral the location is divided into axillary and adnexal.

Axillary buds are formed in the axils of the leaves, their number corresponds to the number of leaves on the stem, and adnexal buds are located on the internodal areas, roots, leaves. With their help, vegetative propagation of plants is carried out.

Stem Growth Types

Plants are found with upright stems - grow perpendicular to the soil (sunflower, birch);

Creeping- spread over the ground, rooting in nodes (strawberries);

curly- also creep along the substrate, but do not take root in the nodes (hops);

climbers having tendrils (you can recall the movie "Jack and the Beanstalk" and the characteristic appearance of the stem of a bean plant, which, branching, reached the heavens);

shortened dandelion, plantain.

The stem shape is:

• cylindrical;
• trihedral;
• multifaceted;
• flattened.

stem branching

Increasing the size of a plant increases its nutrient and energy requirements. Therefore, the stem starts branching to increase the number of leaves and perform more photosynthetic processes. Stems of the second order are formed on the trunk, of which - the third, and so on. According to the type of branching, plants are divided into:

dichotomous- at the same time, the main trunk gives two shoots, which are also divided into two, and this is how multiple division occurs.

False dichotomous- the branches begin to grow from the lateral buds, which are located on the opposite side of the stem.

Monopodial- the main massive axis of the plant stands out, from which there are lateral branches.

Sympodial- the stem of the first order dies off or its axis ends with a flower, then growth continues due to the escape from the underlying bud.

Depending on the structure of the stem, the following are distinguished plant forms:

Herbs- have non-lignified stems, the life cycle of which lasts one growing season.

Trees- perennial plants with a lignified trunk.

shrubs- a large number of lignified trunks sprout from the root.