BRANCHING OF THE SHOOTS AND THE STRUCTURE OF THE STEM OF SOME SPECIES OF WOODY PLANTS

Ryabova Maria Sergeevna 1 , Shirokova Nadezhda Pavlovna 2
1 Arzamas branch of the UNN N.I. Lobachevsky, student
2 Arzamas Branch of the UNN N.I. Lobachevsky, associate professor, candidate of biological sciences

annotation
The article analyzes the type of phyllotaxis and the location of the buds of renewal, the type of branching and growth of shoots, the features of the shape of the crown of five species of woody deciduous plants are noted. The attention of the authors is focused on the analysis of the features of the anatomical structure of the stem of annual shoots. Differences and similarities in the morphology and anatomy of some woody plants associated with their systematic position and life form.

BRANCHING SHOOTS AND STRUCTURE OF THE STEM OF SOME SPECIES OF WOODY PLANTS

Ryabova Maria Sergeevna 1 , Shirokova Nadezhda Pavlovna 2
1 Arzamas branch of the Lobachevsky State University of Nizhni Novgorod (UNN), student
2 Arzamas branch of the Lobachevsky State University of Nizhni Novgorod (UNN), Associate Professor, Candidate of Biological Sciences

Abstract
The article analyzes the type of phyllotaxis and the type of the disposition of the resuming kidneys, the type of branching and growth of shoots. Specific features of the crown shape of the five species of woody deciduous plants are denoted in the article. The authors" attention is focused on the analysis of specific features of the anatomical structure of the stem of annual shoots. Morphological and anatomical differences and similarities of certain woody plants are presented and discussed in the paper. The above mentioned differences and similarities are related to the systematic position and the life form of the plants.

Bibliographic link to the article:
Ryabova M.S., Shirokova N.P. Branching of shoots and the structure of the stem of some species of woody plants // Research in the field of natural sciences. 2014. No. 3 [Electronic resource]..02.2019).

Branching of shoots is the formation of a system of branched axes, due to which the total mass of the aerial part of the plant increases. There are two types of branching: apical (dichotomous) and lateral (occurs due to monopodial and sympodial growth). With dichotomous branching, shoot growth is provided by two initials formed as a result of dividing one. With a monopodial growth method, the apical bud forms the main axis, which grows from year to year, sometimes throughout life, and the main stem develops more strongly than the lateral ones. With sympodial growth, the functional activity of the apical bud is lost, as a result of which the growth of lateral shoots is enhanced. The form of sympodial branching is false dichotomous - the apical bud dies off or simply does not develop, and growth is continued by two lateral buds located oppositely located directly under the apical bud.

In woody plants, as a result of branching of various types, a crown is formed, that is, a set of branches, shoots and leaves. biological significance crown consists in the fact that the entire leaf surface of the plant is concentrated in it, which serves as an apparatus for photosynthesis. It also contains generative organs, that is, flowers and fruits. The shape of the crown is determined by the hereditary nature of plant organisms and reflects the adaptation of plants to the conditions of existence.

The functions of branching and growth of the shoot system of the plant are performed by renewal buds. In winter, under resting buds on leafless branches, you can see a leaf scar - the place of attachment of a fallen leaf, and on it - a leaf trace - a trace from dangling conductive bundles of the covering leaf.

The kidney is a rudimentary shoot. The patterns of laying leaf primordia on the growth cone of the shoot also determine the order in which the leaves are arranged on the stem. Since there are buds in the axils of the leaves, from which lateral shoots develop, the nature of the leaf arrangement largely depends on appearance plants. There are 3 main types of leaf arrangement, or phyllotaxis: opposite, whorled and alternate. Opposite leaf arrangement is characterized by the presence of 2 leaves in the node - one opposite the other. With a whorled leaf arrangement, more than 2 leaves depart from the node. The most common is the next, or spiral leaf arrangement, in which each node has only one leaf.

The stem is an axial, radially symmetrical organ with long apical (apical) growth, carrying out bilateral movement of substances between roots and leaves, supporting the crown of the plant, contributing to an increase in the total assimilation surface of the plant due to branching, participating in the storage of reserve substances, and at a young age - carrying out also photosynthesis. These functions determine the presence in the stem of integumentary, well-developed conductive, mechanical tissues and functionally different parenchyma. The stem consists of functionally different tissues, in the arrangement of which there are certain patterns. An analysis of the literature data showed a poor coverage of knowledge on the anatomy of annual shoots, so the problem of studying the anatomical structure of the stem is very relevant.

Materials and methods of research

Among the huge variety of trees and shrubs, we chose five species of woody plants as objects of study - the heart-shaped linden ( Tilia cordata Mill.), bird cherry ( Padus racemosa L.), black poplar ( Populus nigra L.), common lilac ( Syringa vulgaris L.), horse chestnut ( Aesculus hippocastanum L.). The choice is due to the wide use of plants in the landscaping of the city of Arzamas (55º37´N, 43º78´E) and in the use of these species in environmental studies, for example, small-leaved linden belongs to smoke and gas resistant species.

As a result of the study of the biological characteristics of the selected plants, we analyzed and studied the bud arrangement, leaf arrangement, branching type, crown shape, leaf trace features, and studied the anatomical structure of the stem of the annual shoot. The shape of leaf scars and the number of leaf marks were determined using an MBS-10 binocular. The study of anatomical features was carried out on transverse sections of the stem in the area of ​​internodes prepared with a blade using a Mikmed microscope at a magnification of 10 × 20, 10 × 40. The data were recorded in the form of photographs and diagrams.

Results and discussion

Linden small-leaved ( Tilia cordata Mill.)

According to the location of the terminal buds on the leafless branches of trees and shrubs, it was determined that the small-leaved linden is characterized by lateral branching, sympodial growth. The real apical bud fell off, leaving a small scar; its place was taken by the axillary kidney closest to it. Under the axillary bud, a scar is visible in place of the fallen cover sheet (Fig. 1). The leaf scar is semicircular in shape, located obliquely on one side. The leaf trace is three-beam (Fig. 2).

In the small-leaved linden, the upper branches are directed upwards, the lateral ones grow almost horizontally, at right angles to the trunk, and with aging they go down a little. As a result of such anisotropic growth of shoots, the broad oval crown is inherent in linden. Linden shoots are characterized by another leaf arrangement.

Figure 1 - The final bud of a linden (a) with a leaf scar (b)

Figure 2 - Cross section through a three-beam (a) linden leaf scar

On the surface of the stem of the annual shoot of small-leaved linden, remnants of the dead primary integumentary tissue, the epidermis, have been preserved. As the secondary structure of the axial organs of the plant develops, the epidermis is replaced by the periderm. The periderm phellem is 4-5-layered, represented by square cells (in plan) with thickened membranes. The color of the periderm cells gives the ripened shoot a red-brown color. In the periderm, lenticels are formed through which gas exchange of living tissues takes place. The lenticels are filled with loose performing tissue. Under the periderm there is a mechanical tissue 4 - 5-layer lamellar collenchyma and the main tissue - chlorophyll-bearing parenchyma (Fig. 3). The bast has a clear structure of alternating soft and hard in trapeziums, separated by delatation rays. In linden stems, the fibers are located along the periphery of the phloem. Longline wood - the horizontal layering of tracheal and parenchymal vertical cells is clearly maintained. The wood on the cross section of the annual growth ring is open-porous. Vessels of early wood are not larger or slightly larger than those of late wood, which is consistent with literature data. Linden wood is characterized, in addition to pores, by spiral vessels. The distribution of the axial woody parenchyma in small-leaved apotracheal linden is traction (Fig. 4), while the position of the parenchyma, regardless of the position of the vessels, the cells are grouped in the form of stripes, which is consistent with the literature data. In the wood, radial primary parenchymal rays are also visible, reaching the core of the stem. The core of the stem has the shape of a circle and consists of parenchymal cells of a round-oval shape. The wood in the annual linden shoot has the largest volume compared to the bark and core.

Figure 3 - Cross section of the stem of small-leaved linden

Picture 4 - Small-leaved linden wood (cross section)

Common bird cherry ( Padus racemosa L.)

It was found that the main axis of the bird cherry can grow monopodially for several years due to the apical bud. At 3-5 years of age, the growth of the apex of the main axis stops. Under it, two lateral branches outgrowing it are formed from the lateral buds, growing in the direction of the main axis, a sympodial growth is formed. Under the terminal bud, which is lateral, there is a leaf scar in place of the fallen cover leaf, in the axil of which this bud developed.

In bird cherry, the leaf scar is surrounded by a brown-reddish roller (Fig. 5). The leaf scar is reniform in shape with a three-beam trace. The crown is broadly ovate. In young trees, the branches go up under acute angle, with age they bend down under the action of their own gravity. The arrangement of bird cherry leaves is alternate.

Figure 5 - Leaf three-beam (a) scar (b) bird cherry

The annual stem of bird cherry is covered with a single-layered epidermis, bearing hairs that help protect the stem from dryness or excessive moisture. The periderm comes to replace the single-layer primary integumentary tissue of the bird cherry epidermis. Periderm phellem 4 - 5-layered. Relatively thin-walled phellem cells give the ripened stem of bird cherry a gray-brown color. Under the periderm there are 3 - 4 layers of a continuous lamellar or corner collenchyma (Fig. 6). The phloem is located in a continuous layer. Between the phloem and xylem is the cambium. The wood of bird cherry is closer to the non-tiered species, since the horizontal layers of the tracheal elements have very uneven outlines. On the cross section of the wood, the vessels are distributed evenly over the entire ring, but in early wood there are individual vessels larger than in late wood, that is, the wood is closer to open-pore wood. The axial parenchyma is represented by the apotracheal type, while the parenchymal cells are grouped in the form of stripes, but there are also scattered cells of the parenchyma, therefore, it is of a stranded or diffuse type. On the ring of wood annual escape it is not possible to reliably determine the type of apotracheal wood. Xylem consists of large and small vessels. The central parenchymal cylinder is divided into two zones: external (perimedullary) and internal. Along the edges of the outer zone, 6 traces of primary conductive wood bundles protrude. The inner zone consists of rounded large parenchymal cells.

Figure 7 - Cross section of the bird cherry stem

Poplar black ( Populus nigra L.)

Poplar is characterized by sympodial growth. A distinctive feature of black poplar is the alternation of elongated and shortened shoots (Fig. 8). The elongated shoot is characterized by intensive growth of internodes. A shortened shoot is characterized by inhibited growth of internodes, its axis practically consists of only nodes, closely shifted. The development of shortened shoots results in crown density and, when occupying a relatively small area, very complete coverage of its foliage. The crown is ovoid, broad and spreading.

Poplar has a three-tufted leaf track. The bundles of the leaf trace are connected in pairs. The leaf scar is heart-shaped, or in the form of a crescent (Fig. 9). In poplar, large branches are angled upwards. It was found that black poplar is characterized by the next leaf arrangement.

Figure 8 - Shortened (a) and elongated (b) poplar shoots

Figure 9 - Leaf scar (a) of black poplar with 3 bunches (b)

With secondary changes in the stem of black poplar, by the end of the first year of life, a secondary integumentary tissue of the periderm is formed. Its main part, the cork, consists of two rows of cells. Under the integumentary tissue is a multilayered primary cortex, consisting mainly of parenchymal cells. In the parenchyma there is a mechanical tissue - lamellar collenchyma. Sclerenchymal fibers of recyclic origin are located in a continuous ring.
Following them are the conductive tissues of the phloem and xylem, separated from each other by the cambium. Wood structure on tangential cut non-tiered. Horizontal layers have very uneven outlines. The wood of the annual shoot of poplar is diffusely vascular - with vessels more or less uniform in size and evenly distributed throughout the ring, which is consistent with the literature data. The axial parenchyma is paratracheal and slightly vasocentric, which is consistent with the literature data. Parenchyma cells form a continuous or intermittent lining around the vessels. A distinctive feature of the core cells is their small size and pentagonal arrangement (Fig. 10).

Figure 10 - Cross section of a black poplar stem

Common lilac
(Syringa vulgaris L.)

In lilac, a special form of sympodial growth is expressed - false dichotomous. With this type of branching, the apical bud dies or does not develop. The growth and branching of the axes in the lilac shoot system occurs due to two lateral, terminal, oppositely located buds. One of them is usually larger, has a large capacity. A stronger shoot develops from it, which often continues the maternal axis in the direction of growth. The crown of the lilac is ovoid.

The common lilac has a five-tufted leaf trace, sometimes more. The bundles are arranged crowded in the form of a crescent. Leaf scars of two opposite buds do not touch each other (Fig. 11). The leaf arrangement of common lilac is cross-opposite.

Figure 11 - Leaf scar (a) common lilac with 5 bunches (b)

On a cross section of the annual shoot of common lilac, under the dead epidermis, represented by a single layer of cells, there is a periderm, which replaces the primary surface tissues. The fellema is poorly developed and is represented by a single layer with relatively thin walls. In the periderm, lenticels are formed, filled with performing tissue. Under the layer of periderm is a layer of mechanical tissue - lamellar collenchyma. It is represented by four layers of rectangular cells. Under the collenchyma is the main parenchyma. Sclerenchyma of pericyclic origin, located in strands. After mechanical tissues, there are conductive tissues - phloem and xylem, delimited from each other by an educational tissue - cambium. The structure of wood is similar to longline. The wood is closer to the scattered pore type - the vessels are scattered more or less evenly in the thickness of the growth layer, the size and number of gaps only slightly decrease towards the outer boundary of the annual layer. The cells of the axial parenchyma are grouped in the form of bands. This type of distribution of parenchymal cells is called apotracheal cord. Inside of the conductive tissues is the core, represented by rounded parenchymal cells (Fig. 12).

Figure 12 - Cross section of the stem of common lilac

horse chestnut ( Aesculus hippocastanum L.)

The type of branching of shoots in horse chestnut, like in lilac, is false dichotomous. The horse chestnut crown is spherical. In horse chestnut, the leaf scar is shield-shaped, in the apical bud it is three-bunched, and in the lateral ones it is five-bunched (Fig. 13). Horse chestnut shoots have a cross-opposite leaf arrangement.

Fig.13. Leaf scar (a) horse chestnut with 5 scars (b)

Outside the stem of horse chestnut, there is a secondary integumentary tissue of the periderm, in which a cork (phellem) is well developed, consisting of 5 flattened layers of reddish thick-walled cells, giving the stem an appropriate color. The phellem cells adjoin each other tightly, without intercellular spaces. Under the periderm is the primary cortex, consisting of mechanical tissues: lamellar collenchyma and assimilation parenchyma. In the central axial cylinder, strands of sclerenchyma alternate with parenchyma. Next is the secondary phloem (bast). On the border of the bast and wood is the cambium. Longline wood - horizontal layering is maintained clearly, which is consistent with the literature data.
In early wood, the vessels are larger, the type of wood according to the distribution of vessels is ring-vascular, which is consistent with the literature data. Apotracheal heavy wood with scattered elements. In the xylem, spiral vessels are expressed along with other types. The center of the stem is occupied by the core. It consists of parenchymal rounded cells (Fig. 14).

Figure 14 - Cross section of a horse chestnut stem

As a result of the observations, it was found that small-leaved linden and black poplar have a sympodial type of branching. The common bird cherry grows monopodially at first, and then sympodially. Plants characterized by a cross-opposite type of leaf arrangement (common lilac and horse chestnut) have false dichotomous branching.

Features of leaf scars and leaf traces are different for different types of tree species, which is determined by the taxonomy of each species.

As a result of the observations, it was found that the anatomy of the annual shoot of the studied species of woody plants has specific features associated with the systematic position and common features structures due to the life form of the plant and the age of the shoots.

From an evolutionary perspective, longline wood can be considered more highly specialized than non-storywood. Longline wood is typical for linden, lilac and chestnut. The annular pore type of wood seems to be highly specialized and occurs in relatively few species, most of which belong to the inhabitants of the northern temperate zone. Conduction of water in annular pore wood is approximately 10 times faster than in open pore wood. Of the five species of woody plants in the stem of the annual shoot of horse chestnut, the wood resembles annular pore wood in terms of the type of location and size of the diameter of the vessels of early and late wood, and in all other plants it resembles open pore wood.

Bibliographic list

1. Andreeva I.I., Rodman L.S. Botany. – M.: Kolos, 2002. – 488 p.
2. Shirokova N.P. Features of the structure of stems and leaves of some plant species // Modern trends in education and science: a collection scientific papers Based on the materials of the International Scientific and Practical Conference October 31, 2013: in 26 parts. Part 4; M-in arr. and science of the Russian Federation. Tambov: Publishing house of TROO “Business-Science-Society”, 2013. P. 150-153.
3. Fedorov A.A. Atlas of descriptive morphology of higher plants / A.A. Fedorov, M. E. Kirpichnikov, Z. T. Artyushenko - Leningrad: Publishing House of the Academy of Sciences of the USSR, 1956. - 301 p.
4. Lotova L. I. Anatomy and morphology of higher plants - M .: Editorial URSS, 2001. - 528 p.
5. Shirokova N. P., Nedoseko O. I. Selected topics of anatomy and morphology of plants: textbook. Manual - 3rd ed., Revised. and additional - Arzamas: AGPI, 2012. - 169 p.
6. Bukharina I. L., Dvoeglazova A. A. Bioecological features of herbaceous and woody plants in urban plantings. - Izhevsk: Udmurt University, 2010. - 184 p.
7. Esau K. Anatomy of seed plants. T. 1. - M.: Mir, 1980. - 218 p.
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1. What is called an escape?

A stem with leaves and buds on it is called a shoot.

2. What functions do mechanical, conductive, integumentary tissues perform?

Mechanical tissues provide strength to plant organs. They make up a frame that supports all plant organs, counteracting their fracture, compression, and rupture.

Conductive tissues provide the movement of water and dissolved in it nutrients by plant.

Integumentary tissues perform mainly a protective function - they protect plants from mechanical damage, the penetration of microorganisms, sudden temperature fluctuations, excessive evaporation, etc.

3. What stems do the plants you know have?

There are two main types of stems: herbaceous (timothy, lily of the valley, tulip, St. John's wort) and woody (linden, oak, pine).

4. What is the difference between the stems of trees, shrubs, herbs?

Herbaceous stems usually exist for one season. These are tender flexible stems of grass, young shoots of tree species. Woody stems acquire hardness due to the deposition of a special substance, lignin, in the shell of their cells. Lignification occurs at the stems of trees and shrubs starting from the second half of the summer of the first year of their life.

Laboratory work

The internal structure of a tree branch

1. Examine the branch, find lentils (tubercles with holes) on it. What role do they play in the life of the tree?

Lenticels are special formations in the cork tissue of the stem that appear to replace the stomata that were in the epidermis. They serve as fans, with the help of which gases are exchanged between the internal atmosphere of the stem and the surrounding air. In the finished state, they look like small tubercles scattered along the stem and visible to the naked eye. Usually these tubercles have an oblong shape and are elongated along the length of the stem.

2. Prepare transverse and longitudinal sections of the branch. Using a magnifying glass, examine the layers of the stem in sections. Using the tutorial, determine the name of each layer.

3. Separate the bark with a needle, try to bend it, break it, stretch it. Read in the textbook what the outer layer of the cortex is called. What is a lub? Where is it located and what is its significance for the plant?

Young (one-year-old) stems are covered with skin on the outside, which is then replaced by cork.

4. On a longitudinal section, consider the bark, wood, core. Test each layer for durability.

The most durable layer of these is wood (it includes mechanical fabric).

In the center of the stem there is a looser layer - the core, in which nutrient reserves are deposited. It consists of large cells of the main tissue with thin membranes. Some plants have large intercellular spaces between cells. Such a core is very loose.

The cork, consisting of dead cells filled with air, also breaks.

5. Separate the bark from the wood, run your finger over the wood. What do you feel? Read the textbook about this layer and its meaning.

The cambium lies between the bark and the wood. It consists of narrow long cells of educational tissue with thin membranes. It cannot be detected with the naked eye, but you can feel it by tearing off part of the bark from the surface of the wood and running your fingers over the exposed area. At the same time, the cambium cells are torn, and their contents flow out, moistening the wood.

In spring and summer, the cambium divides vigorously, and as a result, new bast cells are deposited towards the bark, and new wood cells towards the wood. This is how the stem grows in thickness. When dividing the cambium, wood cells form much more than bast. In autumn, cell division slows down, and in winter it stops completely.

6. Sketch the cross and longitudinal sections of the branch and sign the names of each part of the stem.

See answer to question #2.

7. Find wood on the saw cut of a woody stem, count the number of growth rings with a magnifying glass and determine the age of the tree.

8. Consider growth rings. Are they the same thickness? Explain how wood formed in spring differs from wood formed later in the year.

9. Determine which layers of wood are older in age - lying closer to the middle or to the bark. Explain why you think so.

The layers of wood lying closer to the middle are older. The layers of wood that are closer to the bark are young (between the wood and the bark there is a cambium, which forms new rings).

Questions

1. What is the internal structure of the stem of a tree or shrub?

On the cross section of a tree or shrub, it is easy to distinguish the following areas: bark, cambium, wood and core.

2. What is the importance of peel and cork?

Peel and cork - integumentary tissues. They protect the stem cells located deeper from excessive evaporation, various damages, from the penetration of atmospheric dust with microorganisms that cause plant diseases.

In the skin of the stem, there are stomata through which gas exchange occurs. In a traffic jam, this function is performed by lentils.

3. Where is the bast located and what cells does it consist of?

The inner layer of the bark is called the bast. It consists of sieve tubes and satellite cells, thick-walled bast fibers, as well as groups of cells of the main tissue.

Sieve tubes are a vertical row of elongated living cells, in which the transverse walls are pierced with holes (like a sieve), the nuclei in these cells have collapsed, and the cytoplasm is adjacent to the membrane. This is a conductive tissue of the bast, along which solutions of organic substances move. Sieve tubes are kept alive by companion cells.

Bast fibers - elongated cells with destroyed contents and lignified walls - represent the mechanical tissue of the stem. In the stems of flax, linden, and some other plants, the bast fibers are especially well developed and very strong.

4. What is a cambium? Where it is located?

Cambium is an educational tissue, due to which the stem grows in thickness. In spring and summer, the cambium divides vigorously, and as a result, new bast cells are deposited towards the bark, and new wood cells towards the wood.

The cambium lies between the bark and the wood.

5. What layers are visible on the cross section of the stem when viewed with the naked eye and with a microscope?

On the transverse section of the stem, when viewed with the naked eye, it is easy to distinguish the following areas: bark, cambium, wood and pith. Using a microscope, you can distinguish peel, cork and bast in the bark.

6. What are growth rings? How are they formed?

All layers of wood cells formed in spring, summer and autumn make up the annual growth ring. Small autumn cells are different from the large spring wood cells of the next year, located next to them. Therefore, the boundary between adjacent growth rings on the cross section of wood in many trees is clearly visible.

Think

What can be determined from annual rings? Why do many tropical plants have no growth rings?

By counting the number of growth rings with a magnifying glass, you can determine the age of a cut tree or a cut branch.

By the thickness of the growth rings, you can find out in what conditions the tree grew in different years life. Narrow growth rings indicate a lack of moisture, the shading of the tree and its poor nutrition.

In many tropical plants, growth rings are not visible, because. the conditions there do not differ according to the seasons of the year and are almost always favorable.

Tasks

2. Determine the age of any cut tree from the growth rings. Draw a saw cut. Indicate in the picture the side that the tree was facing north.

Under the tall, gloomy old Poplars, important documents were signed and oaths were pronounced.

In the era of revolutions, the poplar was a symbol of the struggle of the people for freedom and rights.

At the same time, in Chinese traditions, the tree meant the unity of opposites - yin and yang. Thanks to their colors, Poplar leaves represented black and white, the beginning and the end.

In folk tales, Poplar personified a gentle and delicate nature. Poplar leaves, like Aspen, trembled in the wind.

Since ancient times, it was believed that Poplars are able to absorb negative energy and protect the house from evil spirits. Like guards, tall trees stood on the streets in cities and villages. Many old-timers believe that trees cannot endlessly absorb evil thoughts and, in the end, give a lot to the world.

poplar names

There are several theories about the origin of the word "poplar".

According to one version, the tree could be called "Popol", which is derived from the Latin name for the tree "populus". At some point, the word changed for unknown reasons.

The word "populus" from Latin actually means "people".

Where poplar grows

There are about 90 species of this tree. One of the rarest, listed in the Red Book is the Black Poplar.

Poplar belongs to the willow family. In nature, it can be found along the banks of rivers and on the slopes of hills, however, it is most often found along roads and in parks in cities and villages.

Wild species are extremely sensitive to soil moisture. That is why Poplars are not found near swamps and swamps. Cultivated plants, on the contrary, take root well in almost any soil and even in heavily polluted areas.

Various types of Poplars grow in Siberia, the North-Western part of Russia, on Far East, in America, Mexico, China and even East Africa.

Poplar grows very fast and within 40 years reaches an incredible size. The maximum age of such Poplar reaches 150 years. There are cases when the age of the Black Poplar was about 400 years.

What does Poplar look like?

Poplar is a slender tall tree with a strong thick trunk and a silvery crown. The height of the Black Poplar sometimes reaches 40 meters, while the maximum recorded girth of the trunk is more than 4 meters.

Poplar's crown is very dense and broad. Over time, many branches dry up. It is as if negative energy is drying up an old tree from the inside.

The bark of the common poplar has a grayish tint and cracks over time.

The tree is dioecious. female flowers turn into the same poplar fluff in the summer - White snow against the backdrop of a hot summer.

When poplar blossoms

The flowering of Poplar begins in April or May, depending on the region. Due to the high content of pollen in the flowers, the tree is considered an excellent honey plant.

In June and July, ripe fruits with seeds are separated from the branches and spread through forests, cities and parks.

Healing properties of Poplar

The bark, seeds and buds of the plant are used as medicines.

Poplar bark contains tannins, glycosides and alkaloids. Due to this, a decoction of the bark has a sedative effect and calms the nervous system.

At the same time, tannins have an astringent effect and are effective for indigestion.

Decoctions from the kidneys effectively fight inflammation and increase the body's resistance.

An infusion of poplar leaves is used as a wound healing agent.

There are preparations based on Poplar that can cope with a depressive state and normalize sleep.

Poplar buds, powdered and mixed with other ingredients, are used for hair loss. This ointment is able to stimulate the hair follicles.

Contraindications

Tannins in preparations from Poplar bark can aggravate the condition of the problematic gastrointestinal tract.

It must be remembered that the use of any properties of Poplar for medicinal purposes, like any other plant, is possible only after consultation with specialists.

Poplar Application

Poplar wood is used in industry as a raw material for making paper, matches, plywood and even charcoal.

Despite the fact that poplar wood is not a favorite material for carvers and joiners, it is very valuable. The tree is able to quickly reach its maturity, therefore it is an important and fast source of renewable natural resources.

Poplar is capable of producing great amount oxygen and surpasses even Pine and El.

Many plant species are unpretentious in the soil and are able to withstand increased air pollution by converting carbon dioxide into oxygen. That is why this plant has been planted in parks and along roads for many decades in a row.

Unfortunately, Poplar is also known for being a strong irritant for allergy sufferers. This fact was clearly not taken into account in Soviet times during mass landings of Poplars in residential areas.

The oldest Poplar grows in Ukraine. Its age is approximately 200 years, while the girth of the trunk is just over 9 meters.

During the hungry war years, the bast layer under the tree bark was dried and added to flour for baking bread.

As you know, the living layer of a tree is a valuable source of microelements, therefore it was often an assistant in the fight against hunger in the most difficult times in the history of the country.

Poplar bark is very light, so it was often used as a float in fishing nets.

Poplars love to change their gender. Female catkins may form on the male plant. Scientists explain this phenomenon by unfavorable ecology.

The stem is the axial part of the shoot of the plant, it conducts nutrients and brings the leaves to the light. Reserve nutrients can be deposited in the stem. It develops leaves, flowers, fruits with seeds.

The stem has nodes and internodes. A node is a section of a stem containing a leaf(s) and a bud(s). The section of the stem between adjacent nodes is an internode. The angle formed by the leaf and stem above the node is called the leaf axil. The kidneys, which occupy a lateral position on the node, in the axil of the leaf, are called lateral or axillary. At the top of the stem is the apical bud.

The stems of woody and herbaceous plants differ in life expectancy. Above-ground shoots of temperate grasses live, as a rule, for one year (the life span of the shoots is determined by the life span of the stem, the leaves may be replaced). In woody plants, the stem exists for many years. The main stem of a tree is called a trunk; in shrubs, individual large stems are called stems.

There are several types of stems.

upright many woody and herbaceous plants have stems (they usually have shoot growth directed upwards, towards the sun). They have a well-developed mechanical tissue, they can be lignified (birch, apple) or herbaceous (sunflower, corn).

Creeping stems creep along the ground and can take root at the nodes (creeping tenacious, strawberries).

Climbing and climbing stems, united in a group of vines, are very common. Among the vines there are woody and herbaceous. Due to the insufficient development of reinforcing elements, due to the speed of growth, they need supports. Curly shoots spirally wrap their stems around the support, and in some plants the turns of the spiral are directed clockwise, while in others they are counterclockwise. There are also neutral plants, the stems of which curl both to the right and to the left.

curly the stems, rising up, wrap around the support (field bindweed, hops).

clinging the stems rise up, clinging to the support with antennae (mouse peas, grapes).

stem shapes

If we cut the stem across, we will see that in the cross section the stem is most often rounded in outline, with a smooth or ribbed edge. But there may be another: trihedral (in sedge), tetrahedral (in nettles), multifaceted (in many cacti), flattened or flat (in prickly pear), winged (in sweet peas).

Broad flat stems, strongly furrowed, often represent an abnormal growth of tissues. In cereals, the stem (aerial part) is called a culm. It is usually hollow in the middle (except for knots). Hollow stems are common in the Umbelliferae, Cucurbitaceae, and other families.

The internal structure of the stem

Young (one-year-old) stems are covered on the outside with a skin, which is then replaced by a cork consisting of dead cells filled with air. Peel and cork are integumentary tissues.

Cork- multi-layer integumentary fabric. It appears already in the first year of the escape life. With age, the thickness of the cork layer increases. Cork cells are dead, filled with air, tightly adhering to each other. Reliably protects the internal tissues of the stem from adverse conditions.

The peel and cork protect the deeper cells of the stem from excessive evaporation, various damage, from the penetration of atmospheric dust with microorganisms that cause plant diseases.

In the skin of the stem there are stomata through which gas exchange occurs. Lenticels develop in the cork - small tubercles with holes. The lenticels are formed by large cells of the underlying tissue with large intercellular spaces.

Bark- under the integumentary tissue is the bark, the inner part of which is represented by the bast. The composition of the bast, in addition to sieve tubes and satellite cells, includes cells in which reserve substances are deposited.

Bast fibers, elongated cells with destroyed contents and lignified walls, represent the mechanical tissue of the stem. They give the stem strength and increase fracture resistance.

sieve tubes- this is a vertical row of elongated living cells, in which the transverse walls are pierced with holes, the nuclei in these cells have collapsed, and the cytoplasm is adjacent to the membrane. This is a conductive tissue of the bast, along which solutions of organic substances move.

Cambium- narrow long cells of educational tissue with thin membranes. In spring and summer, the cambium cells actively divide - the stem grows in thickness.

The dense, widest layer - wood - is the main part of the stem. Like the bast, it consists of different cells different shapes and sizes: vessels of conductive tissue, wood fibers of mechanical tissue and cells of the main tissue.

All layers of wood cells formed in spring, summer and autumn make up the annual growth ring.

Core- the cells are large, thin-walled, loosely adjacent to each other and perform a storage function.

From the core in the radial direction through the wood and the bast, core rays pass. They consist of cells of the main tissue and perform storage and conduction functions.

Skin		Young (one-year-old) stems are covered on the outside with a skin, which is then replaced by a cork consisting of dead cells filled with air. Peel and cork are integumentary tissues.
Stoma		In the skin of the stem there are stomata through which gas exchange occurs. Lenticels develop in the cork - small tubercles with holes. The lenticels are formed by large cells of the underlying tissue with large intercellular spaces.
Cork		Multi-layer cover fabric. It appears already in the first year of the escape life. With age, the thickness of the cork layer increases. Cork cells are dead, filled with air, tightly adhering to each other. Reliably protects the internal tissues of the stem from adverse conditions.
Bark		Under the integumentary tissue is the bark, the inner part of which is represented by the bast. The composition of the bast, in addition to sieve tubes and satellite cells, includes cells in which reserve substances are deposited.
Cambium		Narrow long cells of educational tissue with thin membranes. In spring and summer, the cambium cells actively divide - the stem grows in thickness.
Core		The central part of the stem. The cells are large, thin-walled, loosely adjacent to each other and perform a storage function.
core rays		From the core in the radial direction through the wood and the bast, core rays pass. They consist of cells of the main tissue and perform storage and conduction functions.

General features of the anatomical structure of the stem

The anatomical structure of the stem corresponds to its main functions: conductive - the stem has a well-developed system of conductive tissues that connects all organs of the plant; supporting - with the help of mechanical tissues, the stem supports all above-ground organs and brings the leaf into favorable conditions lighting; growth - in the stem there is a system of meristems that support the growth of tissues in length and thickness (apical, lateral, intercalary).

The apical meristem gives rise to the primary lateral meristem - procambium - and intercalary meristems. As a result of the activity of primary meristems, the primary structure of the stem is formed. It can persist in some plants for a long time. The secondary meristem, the cambium, forms the secondary state of the stem structure.

Primary Structure. In the stem, a central cylinder (stele) and primary bark are distinguished.

The primary cortex is covered on the outside by the epidermis (integumentary tissue), under it is chlorenchyma (assimilative tissue). It can form alternating bands along the stem, with mechanical tissues (collenchyma and sclerenchyma).

The central cylinder is surrounded by a layer of endoderm. The main part of the central cylinder is occupied by conductive tissues (phloem and xylem), which together with the mechanical tissue (sclerenchyma) form vascular fibrous bundles. Inside of the conductive tissues is the core, consisting of non-specialized parenchyma. Often an air cavity forms in the core.

secondary structure- the cambium forms secondary xylem inward, secondary phloem outward. The primary cortex dies and is replaced by a secondary one - this is the totality of all secondary tissues located outside the cambium.

The structure of the stem depends on the habitat conditions and reflects the structural features of a particular systematic group of plants.

The internal structure of the stem (part of the cross section of the stem of a three-year-old linden shoot)

Periderm. The primary integumentary tissue (epidermis) does not function for long. Instead, a secondary integumentary tissue is formed - the periderm, which consists of three layers cells - cork (outer layer), cork cambium (middle layer) and phelloderm (inner layer). For exchange with the environment, there are lenticels on the periderm.

Primary cortex consists of two layers: collenchyma (the layer under the periderm) - mechanical tissue - and the parenchyma of the primary cortex (it can perform a storage function).

Secondary bark(or bast, phloem). Typical structure of bast: sieve tubes, satellite cells, bast parenchyma and bast fibers. Bast fibers form a layer called hard bast; all other elements form a soft bast.

Cambium- educational fabric. Due to the division and differentiation of its cells, bast cells (secondary bark) are formed outside, and wood cells inside. As a rule, wood cells are formed significantly more than bark cells (ratio 4:1). The growth of the stem in thickness occurs due to the activity of cambial cells. The activity of the cambium ceases in winter and resumes in spring.

Wood (xylem)- the main part of the stem. It is formed due to the activity of the cambium from its inner side. Consists of vessels (tracheas), tracheids, wood parenchyma, wood fibers (mechanical tissue). One ring of wood is formed per year. The boundary between the annual rings is clearly visible, because the spring wood, which was formed after the awakening of the cambium, consists of large thin-walled cells, autumn - from smaller, thicker-walled cells. The transition from spring wood to autumn is gradual, from autumn to spring it is always sudden (here the border between annual rings is formed). The age of the plant can be determined from the growth rings of wood. In tropical plants that grow continuously throughout the year, annual rings are completely invisible.

Core- the central part of the stem. Its outer layer (perimedular zone) consists of living parenchymal cells, the central one consists of large cells, often dead. There may be intercellular spaces between core cells. Spare nutrients are deposited in the living cells of the core.

core beam- a series of parenchymal cells that start from the pith and pass in a radial direction through wood and bast in the primary cortex. Their function is conductive and storage.

Stem growth in thickness

Between the bast and wood in the stem is a layer of cambium cells. Cambium is an educational fabric. Cambium cells divide to form new cells that are part of wood and bast. At the same time, the cambium deposits more cells towards the wood than towards the bark. Therefore, the growth of wood is faster than the bast. As a result of the activity of the cambium, the thickness of the stem increases.

Conditions affecting the growth of a tree in thickness

By the thickness of the growth rings, you can find out in what conditions the tree grew in different years of life. Narrow annual rings indicate a lack of moisture, shading of the tree and poor nutrition.

Annual ring is the growth of wood per year. In the inner zone of this ring, closer to the core, the vessels are larger and there are more of them. This is early wood. In the outer zone of the ring, closer to the cortex, the cells are smaller and thicker-walled. This is late wood. In winter, cambial cells do not divide, they are at rest. In the spring, when the buds open, the activity of the cambium resumes. New wood cells appear and, consequently, a new annual ring is formed. Large-cell wood (early) is next to small-cell (late) wood of the previous year. Thanks to this neighborhood, the border with annual growths of wood becomes clearly visible.

Movement of nutrients along the stem

For the normal life of a plant, water and nutrients must be supplied to all organs. One of the most important functions of the stem is transport. It consists in the transfer of solutions from the organs of soil nutrition - the roots and the organs of air nutrition - the leaves to all organs of the plant. This can be easily verified by making longitudinal and transverse sections of the plant stem as shown in the figure.

The entire plant is permeated with conductive tissues. Water with mineral substances dissolved in it moves along one conducting tissue, and a solution of organic substances moves along the other. Conductive tissues are combined into vascular fibrous bundles, often surrounded by strong fibers of mechanical tissue.

Vascular-fibrous bundles run along the entire stem, connecting the root system with the leaves. But in order to finally verify this, it is advisable to do the following experiment.

Target: make sure that the vascular fibrous bundles connect the root system to the leaves.

What we do: put a sprig of the plant for a while in tinted water. In the experiment, it will replace minerals. After 2-3 hours, make a transverse and longitudinal incision.

What we observe: changed its color and became red wood. The bark and core remained unpainted.

Result: solutions of mineral substances, like colored water, rise from the root inside the stem through the vessels of the wood. Vessels pass through the stem, branch into leaves, and branch there. Through these vessels, water with minerals dissolved in it enters the leaves. This is clearly seen in the longitudinal and transverse sections of the stem.

Of great importance for raising water into the stem is the root pressure and the evaporation of water from the leaves. In place of the evaporated water, new water constantly enters the leaves.

Movement along the stem of organic matter

Organic substances are deposited in special storage tissues, some of which accumulate these substances inside the cells, others inside the cells and in their membranes. Substances that are deposited in the reserve: sugars, starch, inulin, amino acids, proteins, oils.

Organic substances can accumulate in a dissolved state (in beet roots, onion scales), solid (grains of starch, protein - potato tubers, grains of cereals, legumes) or semi-liquid state (drops of oil in castor bean endosperm). Especially a lot of organic matter is deposited in modified underground shoots (rhizomes, tubers, bulbs), as well as in seeds and fruits. In the stem, organic substances can be deposited in the parenchymal cells of the primary cortex, medullary rays, and living cells of the pith.

We know that the starch formed in the leaves then turns into sugar and enters all the organs of the plant.

Target: find out how the sugar from the leaves gets into the stem?

What we do: on the stem houseplant(dracaena, ficus) carefully make an annular incision. Remove the ring of bark from the surface of the stem and expose the wood. We will fix a glass cylinder with water on the stem (see picture).

What we observe: after a few weeks on the branch, above the ring, a thickening appears in the form of an influx. Adventitious roots begin to develop on it.

Result: we know that sieve tubes are located in the bast, and since we cut them by ringing the branch, the organic substances flowing from the leaves reached the annular notch and accumulated there.

Soon adventitious roots begin to develop from the influx.

Conclusion: thus, experience proves that organic substances move along the bast.

Deposition of organic matter

Water and mineral salts, absorbed by the roots, move along the stem to the leaves, flowers and fruits. This is an upward current, it is carried out through wood, the main conducting element of which are vessels (dead empty tubes formed from living parenchymal cells) and tracheids (dead cells that are interconnected using fringed pores).

Organic substances formed in the leaves flow into all organs of the plant. This is a downward current, it is carried out along the bast, the main conducting element of which are sieve tubes (living cells interconnected by sieves - thin partitions with holes, they can be in the transverse and longitudinal walls).

In woody plants, the movement of nutrients in the horizontal plane is carried out using heart-shaped rays.

The significance of the storage tissue lies not only in the fact that the plant, if necessary, feeds on these organic substances, but also in the fact that the latter are a food product for humans and animals, and can also be used as raw materials.

Physical and mechanical principles of the stem structure

The body of a plant is a system that strongly depends on the impact on it of various meteorological factors, as well as on the pressure and weight of its own organs, which are constantly changing in connection with growth and development. The plant is constantly exposed to loads, both static and dynamic. He has to experience the action of impact forces at different durations. These forces include winds of varying strength and intensity, rain, hail, snow, and others. During winds, especially storms, the aerial part of the plant is a large sailing surface, and would easily break if there were no adaptations for resistance in the body: strength — protects from breakage its temporary loads. Elasticity provides resistance to bending, tearing. Rigidity is expressed in the fact that the shape does not change significantly from the action of mechanical loads.

Mechanical tissues play a major role in plant strength. Anchoring is achieved at the base of the petioles, branches and at the points of attachment of the roots. The integumentary tissue has strong and thickened walls of the epidermis.

Elastic stability gives resistance when loaded from above on the plant. The stem of a plant branch can bend but not break; for example, vertical branches, weighed down by fruits, bend, give a bend in the form of an arc, but do not break if they have sufficient elastic stability. Straws of rye, wheat, barley give arcuate bends if the ears are filled with full-fledged grain.

Being a single organism, a plant can live only with a combination of these opposite principles (static - requires the distribution of tissues on the periphery, and the resistance of dynamic load requires the distribution of material in the center) of the distribution of tissues of strength.

Probably, no tree is as popular in landscaping city streets, parks and squares as poplar. So familiar to everyone from childhood, and many people remember the song: “Poplars, poplars, lovers in my city ...” Although poplar often causes criticism during the flowering period, when its fluff covers the streets, gets into apartments, flies into the eyes ...

It would seem that what is interesting in it, in such a familiar and simple, and what can we talk about? But let's get to know this plant better, maybe we will find in it something new and still unknown to us.

plant description

In nature, poplars are distributed throughout the northern hemisphere - from China (their ancestral home is located here), throughout Eurasia, there are in America and even in eastern Africa. In total, there are a little more than 100 species of poplars in the world, united in the genus Populus which belongs to the willow family (Salicaceae).

As you can see, the Latin name of the tree itself speaks of its popularity. And it came from Ancient Greece, where already at that time these trees were grown on the streets and squares.

In nature, poplar most often grows near rivers, as it prefers moist soils. For example, aspen can grow on saline lands, and poplar variegated feels good on dune sands. By the way, a forest where many poplars grow is called a poplar forest. One of the main features of these trees is their rapid growth, which has made poplar so popular in urban landscaping.

Poplar does not live long. Usually the growth of a tree slows down by the age of 50, and 60-80 years is the usual duration of its life, although there are species that live up to 150 years. Poplar wood is highly susceptible to various fungal infections, and therefore tree branches break easily, and they themselves are short-lived.

Poplars are solid, large trees, they are 50-60 m tall, but more often they grow up to 40 m. The trunk is quite impressive, it happens that it reaches a meter in thickness. Different types have a crown of different shapes - spherical, oval, pyramidal. The leaves of all poplars are simple, petiolate, usually oval with a pointed tip, sometimes lanceolate or with a notched edge. Most often smooth, but there are also pubescent.

Poplars are mostly dioecious trees. Flowering takes place in early spring, even before blooming or simultaneously with the unfolding of leaves, pollination usually occurs through the wind. Small flowers are collected in inflorescences-earrings, respectively, male and female. Trees begin to bloom and bear fruit at the age of 10 years.

Poplar fruits are small boxes with fluffy hairs. It is they who cause so much anxiety to the inhabitants of cities. Therefore, it is desirable to plant exclusively male plants for landscaping the streets.

Consider some types of poplars.

Fragrant poplar

grows in the eastern part of Siberia Fragrant poplar (Populus Suaveolens). It is also found in Mongolia and northern China.

The light-loving tree reaches 20 m in height, has a dense ovoid-oval crown, a trunk with a light yellowish-gray bark. It got its name for fragrant and resinous (especially in spring) buds and young twigs. The leaves are bright green, leathery and shiny, oval in shape with a sharp tip at the top, rather dense, slightly whitish below. Small flowers form dangling earrings.

A characteristic feature of poplar is its rapid growth at a young age, and due to its exceptional winter hardiness, it is a valuable species for planting greenery in settlements in the northern regions, although its life expectancy is short in the city.

(Populuslaurifolia) widely distributed throughout Siberia. Habitat - river pebble floodplains, can rise to a height of about 1800 m. Unlike the previous species, shade-tolerant.

The tree is quite tall, has a slightly branched tent-like crown. The bark of the dark trunk is cut through deep cracks. The leaves are lanceolate, elongated, dark green and shiny, located on numerous shortened shoots, which is why it seems that they grow in bunches. This gives the tree a very original shape.

Foliagepoplarslaurel. Photo from plantarium.ru

It does not grow as fast as other species, but it is very resistant to urban smoke, winter-hardy and unpretentious.

Black poplar or black poplar

Also found in Russia Poplar black (PopulusNigra). It grows in the regions of the middle zone to Perm, in the south - in the Crimea and the Caucasus, as well as in Central Asia and even in Western Siberia. Osokor can be seen in various reserves of our country.

Prefers light forests growing on sandy loose soils in river valleys. This is a powerful and tall tree with a spreading crown. The bark is covered with cracks young tree light gray, then gradually blackens. The leaves are rhombic, sometimes triangular in shape with a pointed tip, dark green in color, slightly fragrant.

The plant is winter-hardy, drought-resistant, undemanding to living conditions. But on humus-rich, moist soils it will grow faster.

(Populus pyramidalis)- the tree is tall and slender, with a columnar crown, wide at the bottom and gradually tapering upwards, which makes the tree look like a cypress. It is believed that the birthplace of this species is Asia Minor, but it is not known for sure.

The leaves are rhombus-shaped, may be triangular, not very large. The species is not too hardy, but grows well in central Russia and in the south of Western Siberia. Magnificent tree for urban landscaping, good both in groups and in solitary planting, forms beautiful alleys.

In addition, tree wood is very widely used for economic purposes: it is used to make paper and rayon, make simple furniture and various containers, it goes to lumber and much more. And paint is obtained from the leaves and buds of poplar. This is such a wonderful and useful tree - our old friend poplar.