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.
stems of trees 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 around the support with their stems, 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, inner part 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 of different shapes and sizes: vessels of the conductive tissue, wood fibers of the 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 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 - periderm, which consists of three layers of cells - cork (outer layer), cork cambium (middle layer) and phelloderm (inner layer). To exchange with 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 tissue. 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 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 root system with 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, of which some 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, locomotion nutrients in the horizontal plane is carried out with the help of 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 shock forces when different duration them. Such 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 fabrics play leading 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.
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 ensure the movement of water and nutrients dissolved in it throughout the plant.
Integumentary tissues perform mainly protective function- protect plants from mechanical damage, 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. 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 strength.
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 internal structure stem of a tree or shrub?
On the cross section of a tree or shrub, it is easy to distinguish the following sections: bark, cambium, wood and pith.
2. What is the importance of peel and cork?
Peel and cork - integumentary tissues. They protect the deeper cells of the stem 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 of 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.
Black poplar (Populus nigra L.) is a promising object of the domestic flora, preparations from the buds of which reliably exhibit antimicrobial and antifungal effects. As part of the complex processing of raw materials, we proposed to use black poplar shoots as a source of biologically active compounds. The morphological and anatomical-histological features of the structure of one- and two-year-old shoots of black poplar, which are waste when harvesting buds - the target raw material of black poplar, were studied. The features of the anatomical and histological structure, which can be used as diagnostic signs, are revealed. The main diagnostic features are: the presence of a thick cork layer from the surface, angular-lamellar collenchyma in the primary cortex, sclerified parenchyma in the core of the shoot, and the presence of diamond-shaped calcium oxalate drusen. In addition, a feature of the central cylinder of a non-beam structure, which has a pentagon shape in outline, is diagnostic. The data obtained are reflected in the section "Microscopy" in the draft pharmacopoeial article for medicinal plant raw materials "Black poplar shoots".
Poplar black
Populus nigra L.
plant anatomy
diagnostics of medicinal plants
morphological and anatomical analysis
1. Braslavsky V.B., Kurkin V.A., Ryzhov V.M., Khramova K.O. Studying the issues of non-waste processing of raw materials of species of the genus Poplar // Bulletin of the Samara Scientific Center Russian Academy Sciences. - 2012. - V. 14, No. 1(9). – S. 2181–2183.
2. State Pharmacopoeia of the USSR: in 2 volumes - 11th ed. - M.: Medicine, 1987. - T.1. – S. 290–292.
3. State register medicines. V.2: Typical clinical and pharmacological articles Official publication (as of April 01). - M., 2008. - S. 872-873.
4. Kurkin V.A., Braslavsky V.B., Zapesochnaya G.G., Balmasova I.P., Bakulin V.T., Zhdanov I.P., Pravdivtseva O.E., Filatova N.V. Plants of the willow family - a promising source of new antimicrobial, anti-inflammatory and tonic drugs // Search, development and implementation of new drugs and organizational forms of pharmaceutical activity: Proceedings of the international scientific conference. - Tomsk, 2000. - S. 42-43.
5. Kurkin V.A. Pharmacognosy: a textbook for students of pharmaceutical universities (faculties). - 2nd ed., revised. and additional - Samara: LLC "Etching"; GOU VPO SamGMU Roszdrav, 2007. - 1239 p.
6. Kurkin V.A., Petrukhina I.K. Actual aspects of the creation of import-substituting medicinal herbal preparations // Fundamental research. - 2014. - No. 11(2). - S. 366-371.
7. Patent of the Russian Federation No. 2135201 for the invention "Method of obtaining poplar tincture for the treatment of purulent-inflammatory diseases of soft tissues" / Kurkin V.A., Braslavsky V.B., Zapesochnaya G.G., Pravdivtseva O.E., Zhdanov I. P., Kosyakin V.A., Tkachenko A.A. - A 61 K 35/78. Bull. No. 3 dated August 27, 1998 - 6 p.
8. Potanina O.G. Improving the standardization and quality control of medicinal plant raw materials and dosage forms from it based on the microscopic method of research: author. dis. ... cand. farm. Sciences. - M., 2005. - 24 p.
9. Samylina I.A., Anosova O.G. Pharmacognosy. Atlas: tutorial: in 3 volumes - General part. Terms and techniques of microscopic analysis in pharmacognosy. - M.: GEOTAR-Media, 2007. - 384 p.
10. FS 42-0073-01. Pinostrobin - standard sample (5-Hydroxy-7-methoxy-2-phenylchroman-4-one) / Kotelnikov G.P., Bykov V.A., Arzamastsev A.P., Bagirova V.L., Kurkin V.A. ., Braslavsky V.B., Zapesochnaya G.G. - M.: Pharmacopoeial State Committee of the MZRF, 2001. - 5 p.
11. FSP 42-0329168201. Poplar buds, "angro" / Zakharkin N.I., Bagirova V.L., Kurkin V.A., Braslavsky V.B., Zapesochnaya G.G. and others - M., MZRF, 2001. - 12 p.
Morphological and anatomical analysis of medicinal plant materials (MPR) is one of the most important stages of standardization and confirmation of its authenticity in pharmaceutical analysis. This determines its relevance for modern pharmacy in the study of the morphology and anatomy of new promising types of medicinal herbs in order to further develop regulatory documentation for it.
From our point of view, shoots of black poplar (Pоpulus nigra L.) are such a new and promising VP.
Previously, we (V.A. Kurkin, V.B. Braslavsky, V.M. Ryzhov et al., 2013) conducted a number of studies to study the issues of complex processing of bark and shoots the specified plant as waste obtained during the harvesting of raw materials targeted for poplar - buds. The conducted studies made it possible to reveal the rich flavonoid composition of the studied objects, which confirmed the prospects for their further study and subsequent introduction into pharmaceutical and medical practice. To do this, it is necessary to solve a number of key scientific and organizational issues, in particular, the development of the “Microscopy” section in the draft pharmacopoeial monograph (PS) for a new MP.
The aim of the study was to study the morphological and anatomical and histological features of the structure of black poplar shoots as a waste product obtained during the preparation of the target medicinal plant material "Black poplar bud".
Materials and methods of research
The material for the study was the shoots of black poplar, harvested in March - April 2012-2013 in the village. Alekseevka Samara region on the banks of the Samarka River. The morphological features of the object were assessed visually and with a magnifying glass (×10). The study of anatomical and histological features of the samples was carried out by bright-field microscopy in transmitted and reflected light using microscopes of the Motic brand DM-39C-N9GO-A and DM-111-Digital Microscopy, with a magnification of ×20, ×40, ×100, ×400 .
The preparation of micropreparations and histochemical reactions were carried out, guided by the general pharmacopoeial article on shoots and bark of the State Pharmacopoeia of the USSR, XI edition.
Research results and discussion
Morphological and anatomical analysis was performed on black poplar shoots of the first and second years of vegetation with a cross-sectional diameter of 1.6-2.5 and 4.5 mm (Fig. 1). The indicated diameters are the main ones in the phytomass of shoots obtained by pruning black poplar at the time of harvesting its target MPRS - buds.
Shoots of black poplar with a diameter of 2.5 mm are branches up to 15 cm long, covered with yellow-gray bark (Fig. 1, A). Internodes short, 0.5 to 3 cm long. The nodes protrude noticeably above the internodes with large diameters. The color of the bark at the nodes is dark brown.
Shoots with a larger cross-sectional diameter of 4.5 mm reach a length of 25 cm (Fig. 1, B). They are covered with light gray bark. yellow shades. The morphology of nodes and internodes is similar to those described above for thinner shoots.
Rice. 1. Black poplar shoots: a - diameter = 1.6 - 2.5 mm; b - diameter = 4.5 mm
Anatomically, shoots up to 2.5 mm in diameter are branches of the first year of vegetation of a non-beam type of structure (Fig. 2, A).
From the surface, annual shoots are covered with epidermis, under which a cork layer is formed. The periderm to the total diameter of the considered stem occupies about 10% with a thickness of up to 167 microns. The layer of the primary crust is significant (23%) and reaches a thickness of 380 µm.
The phloem part is less pronounced (16% - 267 microns). The xylem is more developed than the phloem (22%), about 367 µm thick (Fig. 2, A, B). The core of the analyzed shoot is developed significantly (29%), its radius is up to 480 µm (Fig. 2, B).
The epidermis of annual shoots in the cross section is represented by small rounded cells with a diameter of about 16 µm. Remains of the protoplast are visible in the cavity of the cells. Cell walls are thickened unevenly. From the surface, thickenings are significant. The inner cell walls are thickened weaker.
The epidermal cell walls are initially weakly yellow color, visually stand out against the background of a colorless cork. When micropreparations are treated with a 5% alkali solution, the cell walls of the epidermis turn orange-yellow, which indicates the phenolic nature of its pigments (Fig. 2, C). Treatment with a 5% solution of Sudan III reveals the epidermal cell wall, staining it in the characteristic Sudan pink color(Fig. 2, D).
Rice. Fig. 2. Histology of cross sections of black poplar shoots (d = 1.6 - 2.5 mm): A - general form, unstained preparation (x40); B - general view, stained with a solution of aniline sulfate (x40); B - Cork fragment, treated with 5% alkali solution (x400); D - cork fragment, stained with Sudan III solution (x400); E - sclereids of the primary cortex (400); E - sclerenchyma (x400); W - core (x100); Z - core (x400). Designations: 1 - cork; 2 - sclerenchyma; 3 - core; 4 - core sclereids; 5 - xylem; 6 - phloem; 7 - cuticle; 8 - epidermis; 9 - cork cells; 10 - angle-lamellar collenchyma; 11 - sclereids of the primary cortex; 12 - parenchyma of the primary cortex; 13 - sclereids of the cortex; 14 - sclerenchyma; 15 - phloem tissues; 16 - core parenchyma; 17 - rhomboid core drusen
Directly under the epidermis is a significant layer of cork tissue, numbering up to five rows of cells. Cork cells are often almost rectangular in shape with slightly sinuous walls. The width of cork cells is up to 25 µm, the length is up to 30 µm. Cell cavities are empty, protoplast remnants are rare. The cell walls are thin, suberinized, which is confirmed by the characteristic coloration upon treatment with Sudan III solution (Fig. 2d).
The layer of angular-lamellar collenchyma, located behind the cork layer, has from 4 to 7 rows of small cells of a rounded, sometimes angular shape, up to 15 microns in diameter. The cavities of collenchyma cells are filled with amorphous protoplast, initially stained brown. The color of the protoplast is enhanced by treatment with a solution of Sudan III. The cell walls of the collenchyma are cellulose, pore channels are not expressed in them (Fig. 2, C, D).
The main tissue of the primary cortex is loose, with a large number of large intercellular spaces. Parenchymal in cross section, the cells have irregular angular outlines. Their cell walls are cellulose and slightly thickened (Fig. 2e). The protoplast is similar to that of previously described collenchyma cells. Star-shaped calcium oxalate drusen are often found in the parenchyma of the primary cortex (Fig. 2e).
The parenchyma is reinforced with randomly arranged groups of sclereids. Sclereids are much larger in size than the cells of the underlying tissue. Their strongly thickened cell walls are lignified, and the cell cavities are slit-like (Fig. 2e). Groups of sclereids along the periphery have a lining of single crystals.
The phloem tissues from the side of the primary cortex are reinforced with an almost continuous ring consisting of large blocks of sclerenchymal fibers (Fig. 2, A, B). Between the sclerenchyma blocks there are cells of the main tissue, as well as single rounded sclereids with wide lumen cavities (Fig. 2, E).
Sclerenchyma fibers are small, almost rounded in cross section, angular, up to 10 µm in diameter. Their cell walls are strongly thickened, with pronounced pore channels. Fiber cavities are slit-like (Fig. 2, E).
The conductive block of the phloem is made up of cells of different sizes, more or less ordered. Large conductive elements of the bast - sieve tubes in cross section have irregular, sometimes crumpled contours of cellulose cell walls. Their diameter varies from 5 to 15 microns. The cells of the medullary rays are noticeably smaller, arranged radially one behind the other, with a dark brown protoplast. The soft bast occasionally contains small groups of sclerenchyma fibers (Fig. 2, F).
The cambium zone is relatively small in thickness, and it is located along the ring, forming the shape of an irregular pentagon, which is very typical for the analyzed shoots (Fig. 2, A, B).
The xylem block repeats the geometric contours of the pentagon along the cambium. Features of the xylem of the analyzed shoot are typical for wood of the annular vascular type (Fig. 2, A, B). The vascular elements in the cross section are rounded, sometimes oval, oriented strictly radially. Their cell walls are markedly thickened and lignified. Vessel sizes increase from the center (10 μm) to the periphery. The largest diameter of the vessels in the stems of the specified diameter does not exceed 40 microns.
The main tissue of the medullary rays consists of small angular parenchymal cells in cross section, with a red-brown pigment in the cavities. The cell walls are cellulose, slightly thickened. Closer to the center, the medullary rays are wide, up to three cells wide. To the periphery, the thickness of the medullary rays narrows to one row of cells.
The cambial woody parenchyma is lignified. Cells sharply angular, almost rectangular. The protoplast in these cells is not diagnosed. The width of the xylem ring is not uniform. In strongly narrowed places, the xylem block is usually represented by parenchymal cells, there are few vascular elements.
The block of the core in young, one-year-old shoots is significantly pronounced. It also has the shape of a pentagon (Fig. 2, A, B).
The main tissue of the core is loose with a large number of intercellular spaces. Parenchymal cells of the core are large, rounded with cellulose, noticeably thickened walls. The protoplast of the cells is amorphous, stained similarly to the protoplast of wood parenchyma cells in a brown-red color. At the core there is a large number of druse of calcium oxalate is stellate, often rhombic in shape (Fig. 2, G, H).
The core parenchyma is reinforced with chaotically arranged rounded groups of sclereids, which are well diagnosed by lemon-yellow staining when treated with 10% aniline sulfate solution (Fig. 2, B).
The differences between shoots with a larger diameter (4.5 mm) and annual shoots are associated with the processes of their vegetation and development and are mainly in the features of the histology of the main blocks of the woody stem.
The analyzed shoots with a diameter of 4.5 mm are biennial, which is easily diagnosed by two annual rings of wood (Fig. 3, A). The xylem part of the central cylinder significantly increases in size relative to the other blocks and occupies about 37% (0.93 mm) of the total diameter of the transverse section. The phloem also increases significantly and occupies 28% (0.7 mm) of the total diameter. As for the primary bark and pith, their sizes practically do not differ from the sizes characteristic of annual shoots (2.5 mm).
Rice. Fig. 3. Histology of transverse and longitudinal sections of black poplar shoots d = 4.5 mm (x40): A - general view of the cross section; B - cork, view from the surface; B - parenchyma of the primary cortex; D - cork, stained with a solution of aniline sulfate; D - phloem, stained with a solution of aniline sulfate; E - xylem, longitudinal section; G - sclerenchyma, longitudinal section, stained with a solution of aniline sulfate; Z - a fragment of the core. Designations: 1 - cork; 2 - parenchyma of the primary cortex; 3 - cork cells; 4 - sclerenchyma; 5 - phloem; 6 - core; 7 - growth rings of xylem; 8 - inner layer of cork; 9, 10 - sclereids; 11 - cells of the main tissue; 12 - collenchyma; 13 - outer layer of cork; 14 - phloem; 15 - xylem cells; 16 - xylem fibers; 17 - point vessels; 18 - Druzes; 19 - sclereids; 20 - single crystals; 21 - cell protoplast; 22 - sclerenchyma fibers; 23 - core parenchyma
The main difference between the block of integumentary tissues of the analyzed shoot is the absence of the primary cover - the epidermis. When viewed from the surface, the cork is represented by wide-lumen thin-walled rectangular cells with sinuous, sometimes crumpled walls (Fig. 3b). The cross section shows that the cork layer is cytologically divided into two parts. From the periphery, the cork layer is also represented by cells different sizes, from 20 to 40 microns in diameter, having a shape from round to rectangular. From the periphery of the cell, the plugs are strongly wavy and sinuous (Fig. 3d).
The inner layers of cork tissue are composed of rectangular cells, more or less the same in size. Remains of the protoplast are visible in their cavities. Cell membranes of the entire cork layer are suberized (Fig. 3d).
Angle-lamellar collenchyma, described for shoots with a smaller diameter, is also characteristic of shoots large sizes. However, the thickness of the collenchymal layer is thinner and does not exceed three rows cells. In addition, collenchyma cells cross sections have a noticeably more elongated shape (Fig. 3, D). The parenchyma of the primary cortex is structured similarly to that in thinner shoots (Fig. 3c).
The phloem part of the central cylinder in two-year-old shoots with a diameter of 4.5 mm is significantly reinforced with sclerenchymal fibers and single sclereids. Sclerenchyma fibers are arranged in three circles. The outer circle from the periphery is represented by large groups of bast fibers. These groups do not coalesce into a monolithic ring and have fragments of the phloem parenchyma between them. The other two circles of sclerenchyma coalesce into monolithic rings. Sclerenchyma fibers of the phloem are lignified and have a crystalline lining composed of calcium oxalate single crystals (Fig. 3, E, G).
Between the rings of sclerenchyma, the conducting elements of the phloem and storage cellular elements are localized. Protoplasts of soft bast cells are brown in color and noticeably pigmented (Fig. 3e).
Xylem tissues do not differ cytologically from those of shoots of smaller diameter. The conducting elements of the xylem are mainly represented by porous vessels (Fig. 3, F).
The core block has similar outlines of a pentagon, typical for shoots of smaller diameter. The main difference between the core of large shoots is a pronounced sclerification of tissues.
The main tissue of the core is localized along the edge of the pentagon and is significantly pigmented, similar to the parenchyma of the phloem and primary cortex. The cells contain many calcium oxalate druses of a characteristic rhombic shape (Fig. 3, H).
The central part of the core pentagon is completely filled with groups of sclereids and rounded sclerified cells of the basal parenchyma. The cell walls of the main parenchyma are markedly thickened, the pores are weakly expressed. The cell cavities contain remains of the protoplast stained brown (Fig. 3, A, H). Sclereids have strongly thickened membranes with pronounced pore canals. The protoplast is absent in the sclereid cavities.
conclusions
As a result of the research, the features of the morphology and anatomy of a new promising plant material - black poplar shoots were studied. The main features that can be used as diagnostic features in determining the authenticity of raw materials are identified.
Such diagnostically significant features of black poplar shoots with a diameter of 1.6-4.5 mm include the following characteristics: typical features wood stem; the presence of epidermis on annual shoots, the walls of which are impregnated with a pigment of a phenolic nature of an initially yellow color; the presence of a well-developed secondary integumentary tissue, represented by a multilayer cork (phellem); reinforcement of the primary cortex with angular-lamellar collenchyma and randomly located large sclereids in the main parenchyma; the presence of an almost continuous ring of sclerenchymal fibers in the pericyclic zone, to the periphery of the phloem; special outline of the cambium zone, xylem block and core in the form of an irregular pentagon; the presence of isolated groups of large sclereids in the core parenchyma of annual shoots and almost complete sclerification of the core of biennial shoots; the presence of large rhombic calcium oxalate drusen in the parenchyma of the primary cortex and core.
The data obtained are included in the "Microscopy" section of the draft pharmacopoeial monograph on black poplar shoots as perspective view LRS.
Reviewers:
Pervushkin S.V., Doctor of Pharmacy, Professor, Head of the Department of Pharmaceutical Technology, Samara State medical University» Ministry of Health of the Russian Federation, Samara;
Avdeeva E.V., Doctor of Pharmacy, Professor, Head of Education, Department of Pharmacognosy with Botany and Fundamentals of Phytotherapy, Samara State Medical University of the Ministry of Health of the Russian Federation, Samara.
The work was received by the editors on April 10, 2015.
Bibliographic link
Kurkin V.A., Ryzhov V.M., Tarasenko L.V., Manzhos K.O. MORPHOLOGICAL AND ANATOMICAL ANALYSIS OF THE SHOOTS OF THE BLACK POPULUS (POPULUS NIGRA L.) AS A PERSPECTIVE SOURCE OF BIOLOGICALLY ACTIVE COMPOUNDS // Fundamental Research. - 2015. - No. 2-15. - S. 3323-3329;URL: http://fundamental-research.ru/ru/article/view?id=37778 (date of access: 04/30/2019). We bring to your attention the journals published by the publishing house "Academy of Natural History"
Poplars - very fast growing, gaining height and leaf mass from the Willow family. Trees grow very quickly for the first 15-20 years of life, but quickly grow old and die. When poplar blossoms, some people rejoice at the white poplar blizzard in the middle of a hot summer, and some suffer from allergies. All types of poplars purify the city air. There are several dozen species of poplars on earth, many of them are hybrids grown through the efforts of dendrologists.
balsamic
The balsam poplar is found in Canada and North America. The usual height is 17-20 m, old fifty-year-old trees often reach a height of 30 m.
The diameter of the sprawling poplar crown is 10-12 m, it is difficult for two people to grab a thick trunk, since its diameter can be up to two meters. At the base of the trunk, the bark of the plant is dark, uneven, in bursting clumsy furrows; higher along the trunk, an elastic, smooth skin of a white-gray shade begins. 
The branches are covered with leaves 5-14 cm long and 4-7 cm wide. The shape of the leaves is rounded at the petiole and wedge-shaped, tapering to a sharp tip, along the edge of the leaves are covered with a finely serrated relief.
The leaf is smooth, with a leathery cool surface and a long dense petiole (2-2.5 cm), the upper part of the leaf is shiny, dark green, the color of the lower plate is gray-green, very light, the skeletal base of the leaf structure is clearly visible from below.
The buds thrown out in the spring are large, elongated, up to 2 cm high. The buds and newly unfolded young leaves are sticky from a sticky resin coating covering them with a pleasant aroma.
A tree is considered an adult only after 5 or 6 years. The type of this poplar is used to create living, windshields for fields and.
It is almost never used for landscaping cities and villages, although it looks very nice in group plantings, consisting of a small group of trees.
bay leaf
Habitat Western and Eastern Siberia, up to the Angara River. Grows in Altai, in the foothills of the Dzungarian Alatau. Distributed in river valleys on pebbles, on mountain slopes, on gravel.
Plant height from 10 to 20 m, trunk thickness up to 1 m in diameter. This type of poplar is not tall, the skeletal branches are sprawling and not numerous, few new, young shoots grow on them during the year. Therefore, the crown of the plant is not dense, slightly sparse.
Did you know? In total, 95 varieties of poplar trees grow on planet Earth.
The skin of the trunk is gray with cracks. The tree is not very demanding on lighting and lives on the poor. The roots of the bay leaf are very deep; it can withstand the long, frost-rich Siberian winters without any problems.
The color of the bark of young shoots is light yellow, they are slightly pubescent. shoots unusual look, and with clearly visible rebrines, growing up, the shoots become rounded in diameter. 
This ribbing of the shoots is due to longitudinal cork-like growths, which is hallmark this type of poplar. The kidneys are oval, sharp, brown-green, elongated, covered with a sticky and pleasantly smelling substance.
The foliage is large, the length of the leaf is 6-14 cm, the width is from 2 to 5 cm. The shape of the leaf is oval-elongated, narrowed towards the end, the leaf has a finely indented border, smooth to the touch, cool, leathery, with a two-tone color (green-whitish). The blossoming foliage is sticky, light green.
Due to the frequent freezing of the branches, an abundant growth of young shoots occurs, from this the crown of the tree seems extremely lush and very decorative.
Flowering in this variety occurs in May-June, fringed earrings have a whitish color, loosely fluffed, covered with yellow pollen.
The male form of the earrings is cylindrical, from 3 to 8 cm long, they have 20-25 stamens with stamen filaments and anthers, the female form of flowering (earrings) has flowers rarely located on them, a pistil with a two-lobed stigma. The blades on the pestle are located downwards. 
After ripening (May-June), in place of inflorescences-earrings, fruits are formed in the form of quadrangular swollen balls. The fully ripened seeds scatter from bursting testicles. Poplars from a number of laurel species are used in plantings along highways.
Important! The poplar family is divided into male and female trees. But only females during flowering spread fluff around.
Pyramidal
The pyramidal poplar is a photophilous plant. Very tall, the description of the species indicates a maximum height of 35-40 m and a maximum lifespan of up to 300 years. It grows in Italy, the Caucasus, Ukraine, Central Asia, Russia.
He likes neutral and slightly acidic, moderately saturated with moisture, but well lit by the sun. Grows fast in the first 10 years. The cap of the plant is narrow, clearly elongated upwards, the branches are powerful, strong, growing at an angle of 90 ° relative to the trunk. 
The diameter of the trunk on the cut is up to one meter, has weakly expressed annual rings, dark gray bark, indented with small cracks. blooms small flowers, collected in long inflorescences in the form of male and female earrings, female earrings are 5-7 cm longer than male ones.
Flowering occurs immediately after bud break. The color of women's and men's earrings is also different, men's - burgundy, women's - light milky.
The young plant has a smooth and elastic, light gray or light olive bark. Leaf shape pyramidal poplar clearly triangular, with a wide even base, sharply tapering towards the top of the leaf.
Like other types of representatives of Willows, the pyramidal has shiny, dark green leaves with a white color along the lower plate, finely serrated along the edge. The leaves are attached to the branches with a short, strong petiole, slightly flattened along.
With the onset of autumn, the foliage turns yellow, in mid-October the leaf cover crumbles to the foot of the trees. 
The roots of this plant are deep down and wide, part of the roots are usually located on the surface of the earth near the base of the tree. It grows well in urban environments, there is no negative reaction to vehicle emissions into the air.
Black (speck)
Poplar black or Osokor - received wide use in Russia and Ukraine, grows in parks and squares, in deciduous forests. It is used in urban landscaping due to its exceptional ability to release oxygen.
One plant can release as much oxygen as 10 and three large, old ones. In one summer season, black poplar purifies the city air from 20 kg of dust accumulations, and its buds also have healing properties and are used in folk medicine. 
During his life, the giant reaches a height of 35 meters, his life span is from 60 to 300 years. Old trees are sprawling, thickset, with a powerful trunk, swollen with skin growths, which eventually hardened and became shapeless-looking wood. The bark is roughly shaped, almost black.
The buds are tightly pressed to the branches, rounded, large, in light scales, covered with gluten. The leaves are hard and large, triangular or diamond-shaped, attached to the branches with flattened cuttings.
Flowering - long earrings, burgundy and yellow, male and female varieties. Male and female blooms differ in color and length of inflorescences, female inflorescences are usually twice as long and lush. 
Flowering occurs in late May or early June. At the end of seed maturation, dispersal (reproduction) begins. Poplar family has earned recognition and love in different parts the globe its diversity, rapid growth and unpretentiousness.
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