SHOOT BRANCHING AND STRUCTURE OF SOME SPECIES OF WOODY PLANTS
Ryabova Maria Sergeevna 1, Shirokova Nadezhda Pavlovna 2
1 Arzamas branch of the UNN named after N.I. Lobachevsky, student
2 Arzamas branch of the UNN named after N.I. Lobachevsky, associate professor, candidate of biological sciences
annotation
The article analyzes the type of phyllotaxis and the location of renewal buds, the type of branching and growth of shoots, the peculiarities of the crown shape of five species of woody deciduous plants are noted. The authors' attention is focused on the analysis of the features of the anatomical structure of the stem of annual shoots. The differences and similarities of morphology and anatomy of some woody plantsrelated to 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 aboveground part of the plant increases. There are two types of branching: apical (dichotomous) and lateral (occurs due to monopodial and sympodial growth). In dichotomous branching, shoot growth is provided by two initials formed by 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, in comparison with the lateral ones, develops more strongly. With sympodial growth, the functional activity of the apical bud is lost, as a result of which the growth of lateral shoots increases. The form of sympodial branching is pseudodichotomous - the apical bud dies off or simply does not develop, and growth is continued by two lateral buds, 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 the crown consists in the fact that the entire leaf surface of the plant is concentrated in it, which serves as the apparatus of photosynthesis. It also houses the 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 living conditions.
The functions of branching and growth of the shoot system of the plant are performed by the buds of renewal. In winter, under the resting buds on leafless branches, you can see a leaf scar - the place of attachment of a fallen leaf, and on it - a leaf trail - a trace from the broken off conductive bundles of the covering leaf.
The kidney is a rudimentary shoot. The patterns of leaf primordia on the shoot growth cone also determine the order of the leaves on the stem. Since there are buds in the leaf axils, from which lateral shoots develop, then the nature of the leaf arrangement depends to a greater extent on external appearance plants. There are 3 main types of leaf arrangement, or phyllotaxis: opposite, whorled and alternate. The 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 an alternate, or spiral, leaf arrangement, in which each node has only one leaf.
The stem is an axial, radially symmetric organ with long-term apical (apical) growth, carrying out a two-way movement of substances between roots and leaves, supporting the plant crown, contributing to an increase in the total assimilatory surface of the plant due to branching, participating in the storage of reserve substances, and at a young age performing also photosynthesis. These functions determine the presence of integumentary, well-developed conductive, mechanical tissues and functionally different parenchyma in the stem. The stem consists of functionally different tissues, in the arrangement of which there are certain patterns. Analysis of literature data showed poor coverage of knowledge on the anatomy of annual shoots, therefore, the problem of studying the anatomical structure of the stem is very urgent.
Materials and research methods
Among the huge variety of trees and shrubs, we selected five species of woody plants as objects of study - heart-shaped linden ( Tilia cordataMill.), 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 the use of these species in environmental studies, for example, the small-leaved linden belongs to the smoke and gas resistant species.
As a result of studying the biological characteristics of the selected plants, we have analyzed and investigated the bud position, leaf position, branching type, crown shape, features of leaf traces, and studied the anatomical structure of the stem of the annual shoot. The shape of leaf scars and the number of leaf traces were determined using an MBS-10 binocular. The study of anatomical features was carried out on transverse sections of the stem prepared with a blade in the area of \u200b\u200binternodes using a Mikmed microscope with a magnification of 10 × 20, 10 × 40. The data were recorded in the form of photographs and diagrams.
Results and their discussion
Small-leaved linden ( Tilia cordata Mill.)
By 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 kidney has fallen off, leaving a small scar; its place was taken by the axillary kidney nearest to it. A scar is visible under the axillary bud at the site of the fallen covering leaf (Fig. 1). A semicircular leaf scar, 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 slightly go down. As a result of such anisotropic shoot growth, the linden tree has a wide-oval crown. For linden shoots, the next leaf arrangement is characteristic.
Figure 1 - Terminal bud of linden (a) with leaf scar (b)
Figure 2 - Cross section through the three-beam (a) leaf scar of linden
On the surface of the stem of the annual shoot of small-leaved linden, the remains of the dead primary integumentary tissue - the epidermis - are preserved. As the secondary structure of the axial organs of the plant develops, the epidermis is replaced by the periderm. Phellema peridermis 4 - 5-layered, represented by square cells (in plan) with thickened membranes. The color of the cells of the peridermis gives the mature shoot a reddish-brown color. Lentils are formed in the periderm, through which gas exchange of living tissues is carried out. The lentils are filled with loose performing tissue. Under the peridermis there is a mechanical tissue of 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 the trapeziums, separated by delatation rays. In linden stems, fibers are located along the periphery of the phloem. Layered wood - horizontal layering of tracheal and parenchymal vertical cells is maintained clearly. The wood on the cross section of the annual growth ring is scattered pore. Early wood vessels are no larger or slightly larger than those of late wood, which is consistent with the literature data. For linden wood, apart from porous, spiral vessels are characteristic. The distribution of the axial woody parenchyma in the apotracheal linden small-leaved is tracheal (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 wood, radial primary parenchymal rays are also visible, reaching the core of the stem. The core of the stem has a circular outline and consists of parenchymal cells of a round-oval shape. The wood in the annual shoot of the linden has the largest volume in comparison with the bark and core.
Figure 3 - Cross section of the small-leaved linden stem
Figure 4 - Small-leaved linden wood (cross section)
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 life, the growth of the top of the main axis stops. Under it, two lateral branches outgrowing it, growing in the direction of the main axis, are formed from the lateral buds; a sympodial growth is formed. Under the terminal bud, which is a lateral one, there is a leaf scar in the place of a fallen covering leaf, in the axil of which this bud developed.
In common bird cherry, the leaf scar is surrounded by a brown-reddish ridge (Fig. 5). The leaf scar is reniform in shape with a three-bundle trace. The crown is broadly ovate. In young trees, branches branch up under acute angle, with age, they bend down under the influence of their own gravity. The arrangement of the leaves of the common bird cherry is alternate.
Figure 5 - Leafy three-bundle (a) scar (b) bird cherry
The annual stem of common bird cherry is covered with a single layer of epidermis, bearing hairs that help protect the stem from dryness or excessive moisture. The single-layer primary integumentary tissue of the bird cherry epidermis is replaced by the periderm. Fellam peridermis 4 - 5-ply. The relatively thin-walled cells of the fella give the mature bird cherry stem a gray-brown color. Under the peridermis there are 3 - 4 layers of continuous lamellar or angular collenchyma (Fig. 6). The phloem is located in a continuous layer. The cambium is located between the phloem and xylem. The wood of the common bird cherry is closer to the non-tiered appearance, since the horizontal layers of the tracheal elements have very uneven outlines. In the cross section of the wood, the vessels are distributed evenly over the entire ring, but in the early wood there are individual vessels that are larger than in the later, that is, the wood is closer to scattered pore. 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 tight or diffuse appearance. On a ring of wood one-year 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 (perimedular) and internal. At 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 stem of the common bird cherry
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. The shortened shoot is characterized by inhibited growth of internodes, its axis practically consists of some nodes, closely shifted. The development of shortened shoots achieves crown density and, when a relatively small area is occupied, a very complete coverage of its foliage. The crown is ovoid, wide and spreading.
The poplar has a three-bundle leaf trail. The bundles of the leaf trail are connected in pairs. The leaf scar is heart-shaped, or in the form of a crescent (Fig. 9). In poplar, large branches are turned upward at an angle. 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, the secondary integumentary tissue of the periderm is formed. Its main part, 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 recycle origin are arranged in a continuous ring.
They are followed by the conducting tissues of phloem and xylem, delimited by cambium. Wood structure on tangential cut non-tiered. The horizontal layers are very jagged. The wood of the annual shoot of poplar is scattered vascular - with vessels that are more or less uniform in size and evenly distributed over the entire ring, which is consistent with the literature data. The axial parenchyma is paratracheal and is poorly vasicentric, which is consistent with the literature data. Parenchymal cells form a continuous or discontinuous 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 the stem of black poplar
Common lilac
(Syringa vulgaris L.)
Lilac has a special form of sympodial growth - pseudo-dichotomous. With this type of branching, the apical bud dies off or does not develop. The growth and branching of the axes in the shoot system of the lilac occurs due to two lateral, terminal, oppositely located buds. One of them is usually larger and has a higher 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-bundle leaf trail, sometimes more. The bundles are arranged in a crowded crescent shape. The leaf scars of the two opposite buds are not in contact with each other (Fig. 11). The leaf arrangement of common lilac is opposite.
Figure 11 - Leaf scar (a) common lilac with 5 bunches (b)
On the cross-section of the annual shoot of common lilac, under the dead epidermis, represented by one layer of cells, is the periderm, which replaces the primary surface tissues. Fellam is poorly developed and is represented by one layer with relatively thin walls. In the periderm, lenticels are formed, filled with performing tissue. Under the peridermis layer is a layer of mechanical tissue - lamellar collenchyma. It is represented by four layers of rectangular cells. The main parenchyma is located under the collenchyma. Sclerenchyma of pericyclic origin, located in strands. After mechanical tissues, there are conductive tissues - phloem and xylem, delimited from each other by educational tissue - cambium. The structure of the wood is similar to tiered. 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 decreases towards the outer boundary of the annual layer. The cells of the axial parenchyma are grouped in stripes. This type of distribution of parenchymal cells is called apotracheal traction. Inside of the conducting tissues is the core, represented by rounded parenchymal cells (Fig. 12).
Figure 12 - Cross section of the common lilac stem
Horse chestnut ( Aesculus hippocastanum L.)
The type of branching of shoots in horse chestnut, like in lilac, is pseudodichotomous. The crown of horse chestnut is spherical. In horse chestnut, the leaf scar is shield-like, in the apical bud it is three-bundled, and in the lateral ones it is five-bundled (Fig. 13). Shoots of horse chestnut have opposite leaf arrangement.
Fig.13. Leaf scar (a) of horse chestnut with 5 scars (b)
Outside the horse chestnut stalk, there is a secondary integumentary tissue of the periderm, in which the cork (fella) is well developed, consisting of 5 flattened layers of reddish thick-walled cells, which give the stalk the appropriate color. Felloma cells adhere tightly to each other, without intercellular spaces. Under the peridermis is the primary cortex, which consists of mechanical tissues: lamellar collenchyma and assimilation parenchyma. In the central axial cylinder, sclerenchyma cords alternate with parenchyma. Next is the secondary phloem (bast). On the border of bast and wood is cambium. Layered 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 pith. It consists of parenchymal rounded cells (Fig. 14).
Figure 14 - Cross section of horse chestnut stem
As a result of the observations, it was found that the small-leaved linden and black poplar have a sympodial branching type. The common bird cherry first grows monopodially and then sympodially. Plants characterized by a crosswise opposite type of leaf arrangement (common lilac and horse chestnut) have pseudo-dichotomous branching.
The 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, layered wood can be considered more highly specialized than non-layered. Layered wood is typical for linden, lilac and chestnut. The ring-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 ring pore wood is about 10 times faster than in scattered pore wood. Of the five species of woody plants in the stem of an annual shoot of horse chestnut, wood resembles ring-pore in the type of location and size of the diameter of the vessels of early and late wood, and in all other plants it is scattered pore.
Bibliographic list
- Andreeva I.I., Rodman L.S. Botany. - M .: Kolos, 2002 .-- 488 p.
- Shirokova N.P. Features of the structure of stems and leaves of some plant species // Modern trends in education and science: collection scientific papers based on the materials of the International Scientific and Practical Conference on October 31, 2013: in 26 parts. Part 4; M-in arr. and science of the Russian Federation. Tambov: Publishing house TPOO “Business Science-Society”, 2013. S. 150-153.
- Fedorov A.A.Atlas of descriptive morphology of higher plants / A.A. Fedorov. Fedorov, M.E. Kirpichnikov, Z.T. Artyushenko - Leningrad: Publishing House of the Academy of Sciences of the USSR, 1956. - 301 p.
- Lotova L.I. Anatomy and morphology of higher plants - M .: Editorial URSS, 2001. - 528 p.
- Shirokova NP, Nedoseko OI Selected topics of anatomy and morphology of plants: textbook. Manual - 3rd ed., Revised. and add. - Arzamas: AGPI, 2012 .-- 169 p.
- Bukharina I. L., Dvoeglazova A. A. Bioecological features of herbaceous and woody plants in urban plantations. - Izhevsk: Udmurt University, 2010 .-- 184 p.
- Ezau 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 located on it is called a shoot.
2. What functions are performed by mechanical, conductive, integumentary tissue?
Mechanical tissues provide strength to plant organs. They constitute a framework that supports all plant organs, resisting their fracture, compression, rupture.
Conductive fabrics ensure the movement of water and dissolved in it nutrients by plant.
Covering tissues perform mainly a protective function - they protect plants from mechanical damage, penetration of microorganisms, sudden temperature fluctuations, excessive evaporation, etc.
3. What stems do you know plants 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, grasses?
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 in the membrane of their cells - lignin. Lignification occurs in the stems of trees and shrubs from the second half of the summer of the first year of their life.
Laboratory work
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?
Lentils are special formations in the cork tissue of the stem that replace the stomata that were in the epidermis. They serve as fans, with the help of which gases are exchanged between the inner 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 are oblong and elongated along the length of the stem.
2. Prepare the cross and longitudinal sections of the branch. Use a magnifying glass to examine the layers of the stem in the slices. Using the tutorial, identify the name of each layer.
3. Separate the bark with a needle, try to bend, break, stretch. Read the textbook for the name of the outer layer of the bark. What is bast? Where is it located and what is its significance for the plant?
Young (annual) stems are covered with skin on the outside, which is then replaced by cork.
4. On a longitudinal cut, examine the bark, wood, core. Test each layer for strength.
The most durable layer of the above 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. In some plants, there are large intercellular spaces between cells. This core is very loose.
The cork of dead cells filled with air also breaks.
5. Separate the bark from the wood, slide your finger over the wood. How do you feel? Read the tutorial about this layer and its meaning.
The cambium lies between bark and 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 ripping 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 rupture, and their contents flow out, moistening the wood.
In spring and summer, the cambium vigorously divides, 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 the cambium is divided, the number of wood cells is much larger than the bast. In autumn, cell division slows down, and in winter it stops completely.
6. Sketch the cross-section and longitudinal section of the branch, and label each part of the stem.
See the answer to question # 2.
7. Find wood on the cut of a tree stem, count the number of tree rings with a magnifying glass and determine the age of the tree.
8. Consider the growth rings. Are they the same thickness? Explain the difference between wood formed in spring and wood from later seasons.
9. Establish 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 in age. The layers of wood that are closer to the bark are young (cambium is located between the wood and the bark, which forms new rings).
Questions
1. What is the internal structure of the stem of a tree or shrub?
On the cross-cut of a tree or shrub, it is easy to distinguish the following areas: bark, cambium, wood and core.
2. What is the significance of the peel and cork?
The skin and cork are integumentary tissues. They protect the stem cells located deeper from excessive evaporation, various damage, from the penetration of atmospheric dust with microorganisms that cause plant diseases.
In the peel 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 bast. It consists of sieve tubes and companion 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 bast tissue, along which solutions of organic substances move. The vital functions of the sieve tubes are provided by companion cells.
Bast fibers - elongated cells with destroyed contents and lignified walls - represent the mechanical tissue of the stem. In stems of flax, linden and some other plants, bast fibers are especially well developed and very strong.
4. What is 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.
Cambium lies between bark and wood.
5. What layers are visible on a cross-section of the stem when viewed with the naked eye and with a microscope?
On the cross section of the stem, when viewed with the naked eye, it is easy to distinguish the following areas: bark, cambium, wood and core. With the help of a microscope, skin, cork and bast can be distinguished in the bark.
6. What are tree rings? How are they formed?
All layers of wood cells formed in spring, summer and autumn form an annual growth ring. Small autumn cells differ from large spring wood cells next year, which are next to them. Therefore, the border between adjacent growth rings on a cross section of wood is clearly visible in many trees.
Think
What can be determined by the growth rings? Why are tree rings not visible in many tropical plants?
By counting the number of tree rings with a magnifying glass, you can determine the age of a sawn tree or branch cut.
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, shading of the tree and its poor nutrition.
In many tropical plants, tree rings are not visible, because conditions there do not differ in seasons and are almost always favorable.
Tasks
2. Determine the age of any tree cut from the tree rings. Draw a saw cut. Indicate in the picture the side that was facing the north of the tree.
Under the tall, gloomy old Poplars, important documents were signed, vows were pronounced.
In the era of revolutions, Poplar was a symbol of the people's struggle for freedom and rights.
At the same time, in Chinese traditions, wood meant the unity of opposites - yin and yang. Thanks to their colors, Poplar leaves represented black and white, beginning and end.
In folk tales, Poplar personified a gentle and subtle 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. As guards, tall trees stood in the streets in towns 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 of the versions, the tree could be called "Popol", which is derived from the Latin name of the tree "populus". At a certain moment, the word changed for unknown reasons.
The word "populus" from Latin actually means "people".
Where does Poplar grow
There are about 90 species of this tree. One of the rarest, listed in the Red Book is Black Poplar.
Poplar belongs to the willow family. In nature, it can be found along river banks 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 moisture in the soil. That is why Poplars are not found near swamps and marshes. Cultivated plants, on the other hand, take root well in almost any soil and even in heavily gassed areas.
Various types of Poplar grow in Siberia, North-Western part of Russia, on Far East, in America, Mexico, China and even East Africa.
Poplar grows very quickly and reaches incredible sizes within 40 years. The maximum age of such a Poplar reaches 150 years. There are cases when the age of Black Poplar was about 400 years.
What does Poplar look like
Poplar is a slender tall tree with a strong, thick trunk and silvery crown. The height of Black Poplar sometimes reaches 40 meters, while the maximum recorded trunk girth is more than 4 meters.
The crown of the Poplar is very thick and wide. Over time, many branches dry out. As if negative energy is drying up an old tree from within.
The bark of 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 sultry summer.
When Poplar blooms
Poplar bloom begins in April or May, depending on the region. Due to the high pollen content in flowers, the tree is considered an excellent honey plant.
In June and July, ripe fruits with seeds are separated from the branches and spread to forests, cities and parks.
The healing properties of Poplar
The bark, seeds and buds of the plant are used as medicines.
Poplar bark contains tannins, glycosides and alkaloids. Thanks to this, the decoction from the bark has a sedative effect and calms the nervous system.
At the same time, tannins are astringent and effective in treating stomach upsets.
Decoctions from the kidneys effectively fight inflammatory processes and increase the body's resistance.
Poplar leaf infusion is used as a wound healing agent.
There are Poplar-based drugs that can cope with depression and normalize sleep.
Poplar buds, ground into powder and mixed with other ingredients, are used for hair loss. This ointment is able to stimulate hair follicles.
Contraindications
Tannins in Poplar bark preparations can aggravate the condition of a 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 industrially as a raw material for the manufacture of paper, matches, plywood and even charcoal.
Although Poplar wood is not a favorite material for carvers and joiners, it is very valuable. The tree can quickly reach its ripeness, therefore it is an important and quick source of renewable natural resources.
Poplar is capable of producing great amount oxygen and surpasses in this even Pine and Spruce.
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.
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 the mass plantings of Poplar in residential areas.
The oldest Poplar grows in Ukraine. Its age is about 200 years, while the trunk girth is just over 9 meters.
In the hungry war years, the bast layer under the bark of the tree was dried and added to flour for baking bread.
As you know, the living layer of the tree is a valuable source of trace elements, 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 floats in fishing nets.
Poplars love to change their gender. Female earrings may form on the male plant. Scientists attribute this phenomenon to unfavorable ecology.
The stem is the axial part of the plant's shoot, it conducts nutrients and brings the leaves to the light. The stem can store spare nutrients. Leaves, flowers, fruits with seeds develop on it.
The stem has nodes and internodes. A node is a section of a stem on which a leaf (leaves) and a bud (buds) are located. 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 sinus. The buds that occupy a lateral position on the node, in the leaf axil, are called lateral or axillary. At the top of the stem is the apical bud.
Stems of woody and herbaceous plants differ in life expectancy. Aerial shoots of grasses of temperate climates live, as a rule, for one year (the lifespan of the shoots is determined by the lifespan of the stem, the leaves may change). In woody plants, the stem has existed for many years. The main stem of a tree is called a trunk; in shrubs, individual large stems are called trunks.
There are several types of stems.
Erect stems are found in many woody and herbaceous plants (their shoot growth is usually directed upward, towards the sun). They have a well-developed mechanical tissue; they can be lignified (birch, apple) or herbaceous (sunflower, corn).
Creeping the stems spread along the ground and can take root in the nodes (creeping tenacious, strawberries).
Climbing and curling stems, united in a group of lianas, are widespread. Among the lianas are woody and herbaceous. Due to the insufficient development of the reinforcing elements, due to the rapidity of their growth, they need supports. Curly shoots spirally twine around the support with their stems, and in some plants the spirals are directed clockwise, while in others - counterclockwise. There are also neutral plants, the stems of which twist both to the right and to the left.
Curly the stems, rising up, twine 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 on the cross section, the stem is most often rounded in outline, with a smooth or ribbed edge. But there may be another: triangular (in sedge), tetrahedral (in nettles), multifaceted (in many cacti), flattened or flat (in prickly pears), winged (in sweet peas).
Wide flat stems, strongly grooved, often represent an abnormal proliferation of tissues. In cereals, the stem (aerial part) is called a straw. It is usually hollow in the middle (except for the nodes). Hollow stems are common in the families of the umbrella, pumpkin, etc.
Internal structure of the stem
Young (annual) stems are covered on the outside with a skin, which is then replaced by a cork consisting of dead cells filled with air. The skin and cork are integumentary tissues.
Bung - multilayer integumentary tissue. She appears already in the first year of the escape's life. With age, the thickness of the cork layer increases. The cork cells are dead, filled with air, tightly adjacent to each other. Reliably protects the inner tissues of the stem from adverse conditions.
The peel and cork 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 takes place. In the cork, lenticels develop - small tubercles with holes. Lentils are formed by large cells of the main tissue with large intercellular spaces.
Bark - under the integumentary tissue is the bark, the inner part of which is represented by the bast. In addition to sieve tubes and companion cells, the bast contains 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 resistance to fracture.
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 bast tissue, along which solutions of organic substances move.
Cambium - narrow long cells of educational tissue with thin membranes. In spring and summer, cambium cells are actively dividing - the stem grows in thickness.
The densest, widest layer is wood - the main part of the stem. Like bast, it consists of different cells of various shapes and sizes: vessels of conducting tissue, wood fibers of mechanical tissue and cells of the main tissue.
All layers of wood cells formed in spring, summer and autumn form an annual growth ring.
Core - cells are large, thin-walled, loosely adjacent to each other and perform a storage function.
From the core in the radial direction, core rays pass through the wood and bast. They consist of cells of the underlying tissue and perform storage and conduction functions.
| Skin | Young (annual) stems are covered on the outside with a skin, which is then replaced by a cork consisting of dead cells filled with air. The skin and cork are integumentary tissues. | |
| Stoma |  | In the skin of the stem there are stomata through which gas exchange takes place. In the cork, lenticels develop - small tubercles with holes. Lentils are formed by large cells of the main tissue with large intercellular spaces. |
| Bung | Multilayer integumentary tissue. She appears already in the first year of the escape's life. With age, the thickness of the cork layer increases. The cork cells are dead, filled with air, tightly adjacent to each other. Reliably protects the inner 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. In addition to sieve tubes and companion cells, the bast contains cells in which reserve substances are deposited. | |
| Cambium | Long narrow cells of educational tissue with thin membranes. In spring and summer, cambium cells are actively dividing - the stem grows in thickness. | |
| Core | 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, core rays pass through the wood and bast. They consist of cells of the main tissue and perform storage and conductive functions. |
General features of the anatomical structure of the stem
The anatomical structure of the stem corresponds to its main functions: conductive - the system of conductive tissues is well developed in the stem, which connects all organs of the plant; supporting - with the help of mechanical tissues, the stem supports all aboveground organs and carries the leaf into favorable conditions lighting; growth - the stem has 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 - the procambium - and the intercalary meristem. As a result of the activity of the primary meristems, the primary structure of the stem is formed. It can persist in some plants for a long time. The secondary meristem - cambium - forms the secondary state of the stem structure.
Primary structure... In the stem, the central cylinder (stele) and the primary bark are distinguished.
The primary cortex is outside covered with epidermis (integumentary tissue), underneath is chlorenchyma (assimilation tissue). It can form alternating stripes 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 mechanical tissue (sclerenchyma) form vascular-fibrous bundles. Inside the conductive tissue is the core, consisting of a non-specialized parenchyma. An air cavity is often formed in the core.
Secondary structure - the cambium forms a secondary xylem inward, and a secondary phloem outward. The primary cortex dies off and is replaced by the secondary - this is the collection of all secondary tissues located outside the cambium.
The structure of the stem depends on the living conditions and reflects the structural features of a particular systematic group of plants.
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 of it, 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). There are lentils on the periderm for exchange with the environment.
Primary cortex consists of two layers: the collenchyma (layer under the periderm) - mechanical tissue - and the parenchyma of the primary cortex (can perform a storage function).
Secondary cortex (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, much more wood cells are formed than bark cells (ratio 4: 1). The growth of the stem in thickness occurs due to the activity of cambium cells. The cambium activity 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 (trachea), tracheids, woody parenchyma, wood fibers (mechanical tissue). One ring of wood is formed per year. The boundary between the growth rings is clearly visible, because the spring wood, which was formed after the awakening of cambium activity, consists of large thin-walled cells, the autumn wood, of smaller, thicker-walled cells. The transition from spring wood to autumn is gradual, from autumn to spring - always sudden (this is where the boundary between the annual rings is formed). By the growth rings of wood, you can find out the age of the plant. In tropical plants that grow continuously throughout the year, the 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 - of large cells, often dead. There may be intercellular spaces between the cells of the core. In the living cells of the core, reserve nutrients are deposited.
Core beam - a series of parenchymal cells that start from the pith and pass radially through the wood and bast in the primary bark. Their function is conducting and storing.
Stem growth in thickness
Between the bast and the wood in the stem is a layer of cambium cells. Cambium is an educational fabric. Cambium cells divide, forming new cells that are part of the wood and bast. In this case, the cambium deposits more cells towards the wood than towards the bark. Therefore, the growth of wood is faster than 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 growth rings indicate a lack of moisture, tree shading and poor nutrition.
Annual ring - this is the increase in 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, cambium cells do not divide; they are dormant. In the spring, with bud opening, cambium activity resumes. New wood cells appear and, therefore, a new growth ring is formed. Large-celled wood (early) is next to small-celled (late) last year. Thanks to this neighborhood, the border with annual growth of wood becomes clearly visible.
Movement of nutrients along the stem
For normal plant life, 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 - roots and organs of air nutrition - leaves to all organs of the plant. This is easy to verify 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 dissolved minerals moves along some conductive tissues, and a solution of organic substances along others. 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 to the leaves. But in order to finally be convinced of this, it is advisable to do the following experiment.
Goal: make sure that the vascular fibrous bundles connect the root system to the leaves.
What we do: put a branch of the plant in tinted water for a while. In the experiment, it will replace minerals. After 2-3 hours, make a transverse and longitudinal section.
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 along the vessels of the wood. Vessels pass through the stem, branch out into leaves, and branch out there. Through these vessels, water with minerals dissolved in it enters the leaves. This is clearly seen on the longitudinal and cross section of the stem.
Root pressure and evaporation of water from leaves are of great importance for raising water into the stem. In place of 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 cells, others - inside cells and in their membranes. Substances that are stored in the stock: sugars, starch, inulin, amino acids, proteins, oils.
Organic substances can accumulate in a dissolved (in beetroot, onion flakes), solid (starch grains, protein - potato tubers, cereal grains, legumes) or semi-liquid (oil drops in the 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 matter can be deposited in the parenchymal cells of the primary cortex, pith rays, and living cells of the pith.
We know that the starch formed in the leaves is then converted into sugar and enters all the organs of the plant.
Goal: to figure out how sugar from the leaves gets into the stem?
What we do: on the stem indoor plant (dracaena, ficus) carefully make a circular incision. Remove the bark ring from the stem surface and expose the wood. We will fix a glass cylinder with water on the stem (see picture).
What we observe: after a few weeks, a thickening in the form of an influx appears on the branch above the ring. Adventitious roots begin to develop on it.
Result: we know that sieve tubes are located in the bast, and since, having ringed the branch, we cut them, the organic matter flowing out of the leaves reached the ring cut and accumulated there.
Soon, adventitious roots begin to develop from the influx.
Output: 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 ascending current, it is carried out through wood, the main conductive element of which are vessels (dead empty tubes formed from living parenchymal cells) and tracheids (dead cells that are connected to each other using bordered pores).
Organic substances formed in the leaves flow into all plant organs. This is a descending current, it is carried out through the bast, the main conductive element of which are sieve tubes (living cells interconnected by strainers - 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 with the help of heart-shaped rays.
The value of the storage tissue lies not only in the fact that the plant feeds on these organic substances, if necessary, 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 structure of the stem
The body of a plant is a system that is highly dependent on the influence of various meteorological factors on it, as well as on the pressure and weight of its own organs, which are constantly changing due to growth and development. The plant is constantly exposed to both static and dynamic loads. He has to experience the action of forces of a percussion nature for their various durations. These forces include winds of varying strength and intensity, rain, hail, snow, etc. the above-ground part of the plant during winds, especially storms, is a large sailing surface, and would easily break if there were no resistance devices in the body: strength - protects against breakage by temporary loads. Elasticity provides resistance to bending, breaking. 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 root attachment. 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 over, but not break; for example, vertical branches, weighed down with 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 arcing bends if the ears are filled with full grain.
As a single organism, a plant can only live with a combination of these opposite principles (static - requires the distribution of tissues at the periphery, and the resistance to dynamic load requires the distribution of material in the center) of the distribution of tissue strength.
Probably not a single tree is as popular as poplar in the landscaping of city streets, parks and squares. Such a familiar to everyone from childhood, and many remember the song: "Poplars, poplars, my lovers in the 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, what is interesting in him, so 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.
Description of the plant
In nature, poplars are distributed throughout the northern hemisphere - from China (their ancestral home is located here), throughout Eurasia, in America and even in eastern Africa. In total, there are slightly 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 variegated poplar does well on the sands of the dunes. By the way, a forest with many poplars is called a poplar. One of the main features of these trees is their rapid growth, which 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, therefore tree branches break easily, and they themselves are short-lived.
Poplars - trees are solid, large, they are 50-60 m tall, but more often they grow up to 40 m. The trunk is quite impressive, it happens, and 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, lanceolate or with a notched edge. More often smooth, but there are also pubescent.
Poplars are mostly dioecious trees. Flowering takes place in early spring, before blooming or simultaneously with the deployment of leaves, pollination usually occurs by 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 bolls with fluffy hairs. It is they who cause so much concern to the inhabitants of cities. Therefore, it is advisable to plant exclusively male plants for landscaping the streets.
Let's consider some types of poplars.
Sweet poplar
In the eastern part of Siberia grows Sweet poplar (Populus Suaveolens). It is also found in Mongolia and North China.
The light-loving tree reaches 20 m in height, has a thick ovoid-oval crown, a trunk with a light yellowish-gray bark. It got its name for the 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 drooping 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 landscaping settlements in the northern regions, although its life expectancy in the city is short.
(PopulusLaurifolia)widespread throughout Siberia. Habitat - river pebble floodplains, can rise to a height of about 1800 m. Unlike the previous species, it is shade-tolerant.
The tree is quite tall, has a slightly branched tent-shaped crown. The bark of a dark colored trunk is cut deep cracks... Leaves are lanceolate, elongated, dark green and shiny, located on numerous shortened shoots, which is why they seem to grow in bunches. This gives the tree a very original shape.
Foliagepoplarslaurel. Photo from the site 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 (Populus Nigra). It grows in the areas 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. It is a powerful and tall tree with a spreading crown. The bark is cracked young tree light gray, then gradually turns black. The leaves have a rhombic, sometimes triangular shape with a pointed tip, dark green, slightly aromatic.
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 upward, which makes the tree look like a cypress. It is believed that the homeland of this species is Asia Minor, but it is not known for sure.
The leaves are diamond-shaped, may be triangular, not very large. The species is not very 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, wood of a tree is very widely used for economic purposes: it is used for the manufacture of paper and artificial silk, simple furniture and various containers are made, it is used for lumber and much more. And from the leaves and buds of poplar they get paint. Here is such a wonderful and useful tree - our old friend poplar.