Figure 36. Anatomical structure of a flat sheet

In monocotyledonous plants, mechanical elements in the leaf are represented by sclerenchyma fibers, in dicotyledonous plants, in addition to sclerenchyma, there is a corner collenchyma, and there may also be stony cells.

The mesophyll occupies the entire space between the upper and lower leaf epidermis, excluding vascular bundles and areas of mechanical tissue. The mesophyll is most often differentiated into palisade (columnar) and spongy parenchyma. Usually, the palisade parenchyma is located under the upper epidermis, and the spongy parenchyma is adjacent to the lower one. In the spongy tissue, the intensity of photosynthesis is lower than in the columnar one, but the processes of transpiration and gas exchange are actively going on here (Fig. 36).

There is a large conducting bundle in the center of the leaf, and smaller bundles on the side. As part of the bundle, the xylem is turned to the top, and the phloem - to the underside of the leaf. Conductive bundles form a continuous system in the leaf, connected with the conductive system of the stem.

In plants, especially woody ones, there are light and shadow leaves. The light ones, located along the periphery of the crown, have a denser network of veins, the upper epidermis covers a thicker cuticle layer than the shadow leaves located inside the crown. In light leaves, stomata are located only in the lower epidermis; columnar chlorenchyma is more developed in them. Shade leaves have a less dense network of veins, stomata - both in the upper and lower epidermis, they have a more developed spongy chlorenchyma.

The anatomical structure of the needle leaf

The epidermis of needles with a highly developed cuticle consists of very thick-walled cells (Fig. 37). Thickened cells of the epidermis significantly strengthen the needles, protect it from excessive evaporation.

The stomata are immersed in special depressions. The shells of the guard cells of the stomata of the needles are lignified. All this has an important adaptive value, since needles, unlike leaves, do not fall off and evaporate moisture all year round.

Figure 37. The structure of the leaf (needles) of Scots pine(Pinus sylvestris) with a centric mesophyll type: A - detailed drawing; B - schematic. 1 - epidermis, 2 - stomatal apparatus, 3 - hypodermis, 4 - folded parenchyma, 5 - resin passage, 6 - endoderm, 7 - xylem, 8 - phloem, 7-8 - vascular bundle, 9 - sclerenchyma, 10 - parenchyma.

Under the epidermis is a continuous layer of highly lignified sclerenchyma fibers, called the hypodermis.

Assimilation tissue of needles of many coniferous trees- this is a fold of yaparenchyma (chlorenchyma).

Conductive tissues are combined into a conductive - central cylinder, i.e., the central part with closed collateral bundles, each of which consists of xylem (wood) and phloem (bast). The conducting cylinder is separated from the chlorenchyma by a number of tightly connected large cells - the parenchymal sheath, which, due to the corking of the radial walls, is similar to the endoderm of the root and therefore bears the same name.

Between the endoderm and the vascular bundles there is a transfusion tissue, consisting partly of dead irregularly shaped cells with bordered pores (tracheid cells), transferring water from the xylem of the vascular bundle to the folded parenchyma (chlorenchyma), and partially of living parenchymal cells that transfer organic substances to the bast of the vascular bundle (sugar) produced by chlorenchyma.

All conifers in the folded parenchyma (chlorenchyma) have large resin passages running along the needles and covered with a sheath of mechanical fibers (sclerenchyma). The number and location of resin ducts play an important diagnostic role in determining species by the anatomical structure of the needles.

EXERCISE

1. Consider, at low magnification, a cross section of a leaf camellia. Draw and label all fabrics.

2. Consider at low magnification a cross-section of the light and shadow leaves of lilac, sketch and mark all tissues.

3. Consider, at low magnification, a cross section of pine needles, draw and label all tissues.

4. Review the tissues of flat and needle leaves (Table 10).

Table 10 Overview of camellia leaf tissues and pine needles

Objects to study: transverse sections of a camellia leaf, light and shadow leaves of a common lilac and needles of a common pine (permanent preparations).

Control questions for the section "Plant Anatomy"

1. What does plant anatomy study?

2. What is the device of the microscope?

3. What are the main provisions of the cell theory.

4. Name the types of plastids.

5. What is a tillakoid?

6. What is a bordered pore?

7. What reserve nutrients in the cell do you know?

8. What is fabric?

9. What fabrics do you know by their functions?

10. What is the function of the cambium?

11. What is the function of wood?

5) absorption of food by absorption (adsorption).

Common with animals is:

1) heterotrophy;

2) the presence of chitin in the cell wall, which is characteristic of the external skeleton of arthropods;

3) the absence of chloroplasts and photosynthetic pigments in cells;

4) accumulation of glycogen as a reserve substance;

5) the formation and release of a metabolic product - urea.

These features of the structure and vital activity of fungi allow us to consider them one of the most ancient groups of eukaryotic organisms that do not have a direct evolutionary relationship with plants, as previously thought. Fungi and plants arose independently of different forms microorganisms living in the water.

More than 100 thousand species of mushrooms are known, and it is assumed that their real number is much larger - 250-300 thousand or more. More than a thousand new species are described worldwide each year. The vast majority of them live on land, and they are found almost everywhere where life can exist. It is estimated that 78-90% of the biomass of all microorganisms in the forest litter is accounted for by the fungal mass (approximately 5 t/ha).

The structure of mushrooms. The vegetative body of the vast majority of fungal species is mycelium, or mycelium, consisting of thin colorless (sometimes slightly colored) threads, or hyphae, with unlimited growth and lateral branching (Fig. 38).

NEEDLES

Accent placement: HVO`YA

NEEDLE, leaves of many gymnosperms and shrubs. X., like a lamellar leaf, performs the functions of photosynthesis and transpiration. Usually the needles are needle-shaped or scaly, less often narrow-lanceolate, dl. up to 20-30 cm (marsh pine); in cross section they are flat, three- or four-sided, semicircular, oval. X. is located spirally, oppositely, whorled (on elongated shoots) or in bunches of 2-50 needles each (on short shoots). In pines, the number of needles in a bunch is systematic. sign. The thick-walled epidermis is covered with a powerful cuticle and bears deeply submerged stomata located in parallel rows along the entire surface of X. Under the epidermis there are sclerophic fibers of the hypodermis (absent in the yew). The mesophyll consists of parenchyma cells (with chloroplasts) and is usually not differentiated into columnar and spongy parenchyma. Assimilation tissue contains resin passages (absent in yew), the number and location of which varies within one species. The conducting fabric is presented by two bunches located nearby in the center, to-rye are surrounded by specific. tissue (transfusion tissue) of tracheids and parenchyma cells and bordered by thick-walled endoderm. X. stays on the plant from 1 year (falls off annually in larch and false larch) to 2-25 years, depending on the species and habitat conditions; dying, it can leave a mark on the shoot - a small flat scar (fir) or a small protrusion of the bark in the form of a pillow (spruce). X. is less diverse in structure and more sensitive to changes in growing conditions and air pollution than the leaves of flowering plants. Total area X. (see Leaf surface index) in cf. 12-18 ha per 1 ha, in some highly productive virgin forests North. America up to 38 ha per 1 ha. Contains (on a dry weight basis) up to 22% cellulose, up to 36% hemicellulose, up to 18% starch, up to 13% protein, up to 14% phenol-carboxylic acid, and a number of other compounds. Releases phytoncides. It is used to obtain coniferous oils (fir oil), chlorophyllocarotene paste, vitamins.

Sources:

1. Forest encyclopedia: In 2 volumes, v.2 / Ch.ed. Vorobyov G.I.; Editorial staff: Anuchin N.A., Atrokhin V.G., Vinogradov V.N. and others - M.: Sov. encyclopedia, 1986.-631 p., ill.

Completed by: O.M. Smirnova teacher of biology Municipal educational institution Uren medium comprehensive school

1.Consider external structure pine shoot. How are the needles on the shoot? What appearance needles? 2. Consider the external structure of the spruce shoot. How are the needles on the shoot? What is the difference between the appearance of spruce needles and pine needles? 3. Examine the micropreparation "Pine needles" under a microscope at first magnification of 56, and then 300 times. On the cross section of the needles, find a dense skin covering the needles from the outside, and stomata in the recesses. Count the number of stomata. 4. Why do pine needles evaporate a lot of moisture?

Pine is a perennial plant reaching a height of 30-40m. The lower parts of the trunks are devoid of branches. In old pines, the first branches begin at a level of at least 10 m from the ground. Pine is very photophilous. Therefore, its lower branches die off quite early. Under the canopy of other trees, it cannot grow and renew itself. Needle-shaped pine leaves - needles - reach 3-4 cm in length. The needles are arranged in pairs on strongly shortened shoots. For the winter, a pine tree, like most coniferous trees, does not fall off the needles, but stays on the plant for 2-3 years. Needles fall along with shortened stems. The needles are covered with thick skin. There are few stomata, they are arranged in rows and are in depressions. There are only two vascular bundles in the leaf, and they do not have lateral branches. Due to these features, pine economically evaporates moisture and easily tolerates drought. The leaves also ate needles, but they are much shorter and more prickly.

A good motive for effective learning activities when practicing botany, it is a regular practice in which children will see in reality what is in the pictures of textbooks. One of the simple first experiments can be the study of a lamellar sheet of any deciduous tree or needles of pine needles under microscope. Due to the simplicity of this work, it will not only develop curiosity and encourage new research, but also teach you to act independently.

pine needles- this is a needle-shaped external organ of a vascular coniferous plant of the "pine" family, which has more than one hundred and thirty known species. In the common people, it is called a “needle”, but from the point of view of botany, it is a pointed and slightly curved leaf with a solid stem-like structure.

The shape is flat or square. If you make a cross section with a microtome and examine pine needles under a microscope, you can visually determine the following structural elements:

1) From four to five rows of unspecialized vesicle cells of the epidermis. This is the skin, the top layer. It carries three functions: protective from the external environment, gas exchange, participation in the process of water movement;

2) The area of ​​the hypodermis. It is located directly under the epidermis, several times thinner than it. This is the result of mitosis of adjacent cell layers;

3) Supporting and storage parenchyma. In fact, this tissue is the core, which is a storehouse of nutrients. Contains vitamins, fats, proteins, also air-saturated intercellular spaces and aquifers. Due to its folded structure and a large number of chloroplasts, the area of ​​​​photosynthesis is significantly increased, in which the collected energy of light radiation is transformed into organic compounds;

4) Endoderm - an internal protective cover, located closer to the axis of the pine needle;

5) Phloem and xylem (conductive tissues). The so-called "phloem juice", which is a solution of sucrose and a small amount of other carbohydrates, is transported to certain areas that consume the products of photosynthesis;

6) Fibrous cells of sclerenchyma. Provide elasticity, protect against deformation, withstanding force effects (for example, when squeezing or bending);

7) Wide vertical and horizontal channels filled with resin - large "resin passages". The mass of resinous resin protects against the penetration of harmful insects (such as bark beetles, weevils).

Needles can be microscoped in transmitted or reflected light. A micropreparation is prepared in a standard way: the taken material is placed on a glass slide, a drop of colorless sticky fir resin is added with a pipette, and covered with a thin cover glass on top. After turning on the backlight and centering on the table, you must then select the search objective of the smallest magnification. When the study drug appeared in the field of view, you can change the magnification to a more powerful one (with refocusing). To obtain a micrograph, you need to display the image on the smartphone screen (an adapter is installed on the eyepiece tube) or on a computer monitor (instead of the eyepiece in this case a video eyepiece with a USB output is inserted).

Suitable models for the observations described above: Micromed C-12, Eureka 40x-400x, Levenhuk Rainbow 2L PLUS.

Core conifers(pine) has a rounded shape with irregular radial outgrowths. It consists of rather large parenchymal cells, having the form of polyhedrons with thin lignified walls; in old trees, these cells are dead, their cavities are filled with air. The core is surrounded by elements formed in the first year of growth that make up the primary wood. The core, together with the adjacent primary wood, is called the core tube. Coniferous wood is characterized by comparative simplicity and correct structure. It consists of only two main elements: the conductive and mechanical functions here are performed by tracheids, and the storage ones are parenchymal cells. On fig. 16 shows a three-dimensional diagram of the microscopic structure of wood of a typical coniferous species - pine.

Tracheids are the main element of coniferous wood. They occupy over 90% of the total wood volume. Tracheids are in the form of strongly elongated spindle-shaped cells (fibers) with thickened lignified walls and oblique ends. On the transverse section, the tracheids are arranged in regular radial rows. The shape of the tracheids in the transverse section is close to rectangular. Tracheids are dead elements; in the trunk of a growing tree, only the newly formed (last) annual layer contains living tracheids, the death of which begins in spring, gradually increases towards autumn, and by the end of winter all tracheids of the last annual layer die off.

Rice. 16. Scheme of the microscopic structure of pine wood: 1 - annual layer; 2 - core beam; 3 - vertical resin passage; 4 - early tracheids; 5 - late tracheids; 6 - bordered time; 7 - beam tracheids; 8 - multi-row beam with a horizontal resin passage.

Within one annual layer, the tracheids of the early and late zones are very different from each other. early tracheids. formed at the beginning of the growing season, perform conductive functions (conduct water), therefore, they have a wide internal cavity and thin walls with numerous pores. Size of early fuck id in the radial direction is greater than in the tangential; the ends of the tracheids are slightly rounded. Late tracheids, deposited by the cambium in the second half of the growing season, are mechanical elements, therefore their walls are greatly thickened due to a sharp decrease in the internal cavity; ends of late tracheids strongly pointed (Fig. 17).
Rice. 17. Tracheids and medullary rays: a-early wood; b - late; pine tracheids from above; core rays on a radial section under a microscope (bottom); on the left - pines; on right -fir; 1 - ray tracheids with small bordered pores; 2 - parenchymal cells with simple pores (large in pine and small in fir). Between the typically early tracheids at the beginning of the annual layer and the typically late tracheids at the end of the layer, there are several rows of tracheids, which, in terms of the thickness of the shells and the size of the cavity, occupy an intermediate position between the early and late tracheids. Such a layer of intermediate tracheids was observed in pine and larch wood. The radial width of early pine tracheids is on average 40 µm, and that of late tracheids is 20 µm; the thickness of the walls of early tracheids is 2 µm, and that of late tracheids is from 3.5 to 7.5 µm. The width of early spruce tracheids from the Arkhangelsk region is on average 45 µm, and that of late tracheids is 22 µm; early tracheal wall thickness id about 3 μ, late - about 5 μ. The length of pine tracheids ranges from 2.1 to 3.7 mm, spruce tracheids - from 2.6 to 5 mm; at the same time, the length of the late tracheids is approximately 10% longer than the early ones. In most of our conifers, the walls of the tracheids are smooth, and only in the yew they have clearly visible spiral thickenings. The thickness of the shells of the pine tracheids at the transition to the late zone first increases, reaching a maximum, and then decreases near the boundary of the annual layer. Thus, the thickest-walled tracheids are not located at the boundary of the annual layers, but in its third quarter. Feature tracheid - bordered pores located mainly on the radial walls at the ends of the tracheids, with which each tracheid is wedged between the neighboring ones, forming a tight connection. Typical fringed pores are present on the walls of early tracheids; late tracheids have smaller pores and in much less quantity. On one early pine tracheid, there are an average of 70 pores, on one late tracheid, only 17 pores; on tracheids of spruce, respectively, 90 and 25; on tracheids of European larch, 90 and 8 pores. Bordered pore diameter different breeds ranges from 8 to 31 μ, the hole diameter is from 4 to 8 μ. Membrane fringed pores in fuck In coniferous species, it has small through perforations of an oval or round shape in the peripheral, unthickened part, facilitating communication between tracheids. When the membrane deviates in one direction or another, the torus closes the pore opening, as a result of which the passage of water through it is very difficult. In heartwood and mature softwood, the fringed pores are essentially out of action. and therefore such wood becomes impervious to water.

The total number of bordered pores in the early wood of spruce tends to increase from the bark to the heartwood, and vice versa in fir. However, the number of closed pores in the wood of both species increases in the direction from the bark to the core, and the sharpest, spasmodic increase in their number is observed when the sapwood passes into ripe wood. At the same time, it was noted that in the late tracheids of the pine kernel there are much fewer closed pores than in the early ones (according to some data, by 8 times), due to which the late zone of the annual layers is impregnated with antiseptics better than the early one. The dimensions of tracheids and the thickness of their walls in the same trunk increase in the direction from the core to the cortex up to a certain age (different in different breeds), after which they remain unchanged or decrease somewhat. The diameter of early pine tracheids reaches a maximum at 40 years of age and then almost does not change.

According to the height of the trunk in mature trees, the length and width of the tracheids in the same annual layer gradually increase from the base of the trunk to the crown, and within the crown they rapidly decrease as they approach the top; the thickness of the walls of the tracheids, on the contrary, first decreases, and again slightly increases in the crown region. In the branches, the tracheids are smaller than in the trunk; branches that radiate from the trunk where the tracheids are longer also have longer tracheids. Growing conditions affect the size of pine tracheids Bryansk region, it turned out that the largest early tracheids and the thickest-walled late tracheids are observed under average, optimal for pine, growing conditions (I-II bonitet); improvement (grade Ia) and deterioration (grade IV) of growing conditions are accompanied by a decrease in the size of early tracheids and the thickness of the walls of late tracheids. Growing conditions mainly affect the wall thickness of late tracheids. and the thickness of the walls of early tracheids almost does not change.

Parenchymal cells in the wood of all conifers make up the core rays, resin canals (in some conifers) and, in some species, the wood parenchyma. The medullary rays of conifers are very narrow (single-row in the transverse section), they consist of several rows of cells in height. In pine, cedar, larch and spruce, the core rays consist of two types of cells: the upper and lower rows along the height of the beam are represented by horizontal (or ray) tracheids with small bordered pores and a characteristic thickening of the walls in some conifers; internal, i.e., medium in height, rows consist of parenchymal cells with simple pores (see Fig. 17). The core rays of fir, yew and juniper consist only of parenchymal cells. The parenchymal cells of the rays of pine and cedar are equipped with one or two large simple pores, while in the rest of our conifers these cells have three to six small simple pores. In pine, cedar, larch and spruce, in addition to single-row rays, there are also multi-row ones, along which horizontal resin passages pass. Radiation tracheids are dead elements, the parenchymal cells of the beam remain alive throughout the sapwood, and sometimes in the core, that is, for 20-30 years.

In a growing tree, along the core rays, nutrients and water move in a horizontal direction during the growing season; during the dormant period, they store reserve nutrients. By the core rays of conifers and hardwood water passes with dissolved sodium phosphate containing a radioactive isotope of phosphorus P 32 .

The resin passage is a narrow long intercellular channel filled with resin, formed by parenchymal cells. Pine, spruce, larch and cedar have resin passages (vertical and horizontal) from our conifers; a number of other conifers (fir, yew, juniper) do not have resin passages in the wood.

Rice. 18. Vertical resin passages on a cross section of pine and larch wood: a-in wood pine freed from resin: b - in pine wood filled with resin; c - in larch: 1 - lining cells; 2 - dead cells; 3 - cells of the accompanying perenchyma; 4-channel stroke; 5 - tracheids; 6 - core beam.

Vertical resin ducts in pine are formed by three layers of woody parenchyma cells: the inner layer; ring of dead cells and outer layer. The inner layer, or epithelium, of the pine resin canal consists of lining cells that look like thin-walled bubbles that protrude into the canal of the resin canal to different depths. When the passage is filled with resin under high pressure, they become flat, and when the passage is empty, they protrude into the channel until they come into contact with each other (Fig. 18). The lining cells of pine have thin cellulose walls and are filled with dense granular protoplasm with a large nucleus; it is these cells that secrete the resin. In spruce and larch, the shell of the lining cells thickens and becomes woody, as a result of which they probably lose the ability to squeeze the resin out of the passage. A ring of dead cells, devoid of protoplasm and filled with air, surrounds the epithelium of the resin duct.

The outer layer is represented by living cells of the accompanying parenchyma with a nucleus, dense protoplasm and spare nutrients(starch, oil). The length of the lining cells on longitudinal sections of wood slightly exceeds the transverse dimensions, the dead cells are narrow and long, and the accompanying cells are several times longer than the dead ones and much wider than them. The lumen (channel) of the vertical resin passage along the tangential direction usually corresponds to four rows of tracheids. With age, the diameter of the vertical resin ducts increases in the direction from the core to the bark. In Siberian larch wood, vertical resin ducts are formed by only one row of lining cells; there is no layer of dead cells, and the accompanying cells are single or absent. In case of damage to a growing tree, the number of resin passages may increase. Horizontal resin ducts run along the medullary rays (Fig. 19) and are usually formed by only two layers of cells: the epithelium and the layer of dead cells.

The length of horizontal passages increases with age as wood and bast grow; their outer end, located in the bast, is closed by the growth of lining cells. The diameter of horizontal resin passages is on average 2.5-3 times smaller than the diameter of vertical passages. In pine, the diameter of horizontal passages is 36-48 μ, in Siberian cedar 48-64 μ, in spruce 20-32 μ, in larch 24-48 μ; on 1 mm 2 of the surface of a tangential cut in pine, spruce and cedar there are from one to three, and in larch from one to four resin passages. Horizontal resin passages intersect with vertical ones (see Fig. 19), forming a single resin-bearing system.

Rice. 19. Resin ducts and cambium cells: a - horizontal resin duct in the core ray of pine; b - connection of vertical and horizontal resin passages on a tangential section of wood; c - shape of cambial cells (scheme); 1 - lining cells; 2 - dead cells; 3 - horizontal stroke channel; 4 - vertical stroke channel; 5 - shape of cambial cells on a tangential section (one-sided and two-sided); 6 - on the radial; 7 - in cross sections.

The number of connections between vertical and horizontal passages reaches several hundred per 1 cm 3 . From this system of connected resin passages, the passages of the nucleus are turned off, which cease to function, as living cells die off; the channels of the passages in the pine are filled with outgrowths of the lining cells. However, in the core of Siberian larch, a large number of resin ducts remain open (their channels are not filled).

Wood parenchyma is not common in coniferous species. Parenchymal cells, somewhat elongated along the length of the trunk, are often connected in rather long rows running in the wood parallel to the axis of the trunk. Among our conifers, pine and yew do not have woody parenchyma. Approximate content various elements in coniferous wood is given in table. 5.

Table 5. The content of various elements in coniferous wood.

		core rays	resin passages	wood parenchyma
Pine (different types)
Spruce (different types)
Western larch
Liesuga
Red cedar
Sequoia evergreen

The cambium consists of a continuous row of narrow, radially flattened, highly elongated living cell stems with wedge-shaped ends. Cambium cells reach their greatest length in conifers. In hardwoods, the length of cambial cells ranges from 0.15 to 0.6 mm. and exceeds the transverse dimensions by several tens of times, while in conifers it can reach 5 mm and exceed the transverse dimensions by several hundred times. The cells contain densely granular protoplasm with a spindle-shaped nucleus. The shape of the cambium cells in three sections is schematically shown in Fig. 19.

In addition to cells strongly elongated along the length, forming fibrous elements of wood and bark, scattered clusters of small parenchymal cells are observed, which form core and bast rays. Located on the border between wood and bark, the cambium covers the entire wood of the tree with a continuous mantle. The activity of the cambium determines the growth of the tree in thickness. During growth, the cambial cells are slightly elongated along the radius of the stem and are divided by tangential septa. One of the formed cells remains cambial, while the other goes to the formation of wood or bark elements. Cell division in the direction of wood occurs 10 times more often than in the direction of the bark, as a result of which the wood grows much faster than the bark.

Cambium works throughout the life of a tree, that is, sometimes hundreds or even thousands of years (sequoia); at the same time, its activity in a temperate climate manifests itself periodically: it freezes for the winter and resumes in the spring, which results in the layering of wood (the formation of annual layers). The activity of the cambium in the spring begins first of all in the thin parts of the trunk and branches, spreading down the trunk, then passes into the roots, first thick and then thin; the end of the activity of the cambium in autumn occurs in the same order.