Osmosis is the diffusion of water through semi-permeable membranes. Osmosis causes the movement of water from a solution with a high water potential to a solution with a low water potential.

Due to the fact that vacuoles contain strong solutions of salts and other substances, plant cells constantly absorb water osmotically and create hydrostatic pressure on the cell wall, called turgor pressure. Turgor pressure is opposed by an equal pressure from the cell wall, directed into the cell. Most plant cells exist in a hypotonic environment. But if such a cell is placed in a hypertonic solution, water will begin to leave the cell according to the laws of osmosis (to equalize the water potential on both sides of the membrane). The vacuole will shrink in volume, its pressure on the protoplast will decrease, and the membrane will begin to move away from the cell wall. The phenomenon of protoplast detachment from the cell wall is called plasmolysis. Under natural conditions, such a loss of turgor in cells will lead to withering of the plant, drooping of leaves and stems. However, this process is reversible: if a cell is placed in water (for example, when watering a plant), a phenomenon occurs that is the opposite of plasmolysis - deplasmolysis

The concept of plant tissues and organs. Classification of plant tissues.

An organ is a part of a plant that performs certain functions and has a specific structure. Vegetative organs, which include the root and shoot, make up the body of higher plants; they provide the individual life of the individual.

In mushrooms and lower plants there is no division of the body into organs. Their body is represented by a system of mycelium or thallus.

The formation of organs in higher plants in the process of evolution is associated with their emergence onto land and adaptation to terrestrial existence.

Fabrics- these are stable, naturally repeating complexes of cells, similar in origin, structure and adapted to perform one or more functions.

According to the functions performed, 6 types of tissues are distinguished: educational (or meristems - from the Greek meristos - divisible) and permanent, including integumentary, basic, mechanical, conductive, and excretory tissues.

A tissue is called simple if all its cells are identical in shape and function (parenchyma, sclerenchyma, collenchyma). Complex tissues (conductive) consist of cells that are unequal in shape, internal structure and function, but are related by a common origin (for example, xylem, formed by the cambium).

There is also a classification of fabrics based on their origin. According to this classification, tissues are divided into primary and secondary.

From the primary meristem, located at the tip of the shoot and at the tip of the root, as well as from the seed embryo, primary permanent tissues (epidermis, collenchyma, sclerenchyma, assimilation tissue, epiblema) are formed. Cells of permanent tissues are incapable of further division. From the cells of a specialized meristem - the procambium - primary conducting tissues (primary xylem, primary phloem) are formed.

From the cells of the secondary meristem are formed: from the cambium - secondary tissues (secondary xylem, secondary phloem), from phellogen - periderm (cork, phelloderm), which appears when the stem and root thicken. Secondary tissues are typically found in gymnosperms and dicotyledonous angiosperms. Powerful Development secondary tissues (wood and bast) are characteristic of woody plants.

Educational fabrics

Educational tissues, due to the constant mitotic division of their cells, ensure the formation of all plant tissues, i.e. actually shape his body.

Integumentary tissues

The cells of the epidermis are tightly closed together, due to which it performs a number of functions:

1) prevents pathogens from entering the plant;

2) protects internal tissues from mechanical damage;

3) regulates gas exchange and transpiration;

4) water and salts are released through it;

5) can function as a suction tissue;

6) takes part in the synthesis of various substances, perception of irritations, and movement of leaves.

Main fabrics

Basic tissues make up the majority of all plant organs. They fill the gaps between conductive and mechanical tissues and are present in all vegetative and generative organs. These tissues are formed due to the differentiation of apical meristems and consist of living parenchymal cells, diverse in structure and function. There are assimilation, storage, air and water-bearing parenchyma.

Photosynthesis occurs in the assimilation, or chlorophyll-bearing, parenchyma. This tissue is found in the aboveground organs of plants (leaves, young green stems).

Storage parenchyma predominates in the stem, root, and rhizome. Storage substances - proteins, fats, carbohydrates - are deposited in the cells of this tissue.

Air-bearing parenchyma, or aerenchyma, consists of air-bearing cavities (intercellular spaces), which are reservoirs for storage gaseous substances. These cavities are surrounded by cells of the main parenchyma (chlorophyll-bearing or storage). Aerenchyma is well developed in aquatic plants in various organs and can be found in land species; its main purpose is to participate in gas exchange, as well as to ensure the buoyancy of plants.

The cells of the aquifer parenchyma contain mucous substances in the vacuoles that help retain moisture. Mostly these cells are found in succulents (cacti, aloe, agave).

Mechanical fabrics

Mechanical tissues are supporting (reinforcing) tissues that form the skeleton of the plant and provide its strength, as a result of which the plant is able to withstand tensile, compressive and bending loads. There are mechanical tissues with uniformly and unevenly thickened cell walls.

Conductive fabrics

Conductive tissues provide upward and downward current to the plant. An upward current is a current of mineral salts dissolved in water, moving from the roots along the stem to the leaves. The ascending current is carried out through the vessels and tracheids of xylem (wood). The downward current is the flow of organic substances directed from the leaves to the roots along the sieve elements of the phloem (phloem).

Conductive elements of xylem. The most ancient conducting elements of xylem are tracheids - these are elongated cells with pointed ends. Tracheids have a lignified cell wall. Based on the nature of the thickening of the shells, the size and location of the sections of the primary shells in them, 4 types of tracheids are distinguished: ringed, spiral, porous and scalariform.

The conducting elements of the phloem in archegonial plants, except mosses, are represented by sieve cells. On their longitudinal walls there are through holes that resemble a sieve, and therefore are called sieve fields. In angiosperms, during the process of evolution, the 2nd type of conducting elements was formed - sieve tubes, which are a longitudinal strand of cells called segments.

Vascular-fibrous bundles. Phloem and xylem form vascular-fibrous bundles, which are located in the central axial cylinder and can be open or closed.

Closed bundles consist of xylem and phloem, between which there is no cambium and, thus, no new phloem and xylem elements are formed. Closed vascular-fibrous bundles are found in the stems and rhizomes of monocots.

Open bundles have a cambium between the phloem and xylem. As a result of the activity of the cambium, the bundle grows and the organ thickens. Open vascular-fibrous bundles are found in all axial organs of dicotyledonous and gymnosperm plants.

Excretory tissues

Excretory tissues are represented by various formations (usually multicellular, less often unicellular), secreting from

plants or isolating metabolic products or water in its tissues. In plants, excretory tissues of internal and external secretion are distinguished.

Osmotic call the phenomena occurring in a system consisting of two solutions separated by a semi-permeable membrane. In a plant cell, the role of semi-permeable films is performed by the boundary layers of the cytoplasm: plasmalemma and tonoplast.

Plasmalemma- the outer membrane of the cytoplasm adjacent to the cell membrane. Tonoplast- inner cytoplasmic membrane surrounding the vacuole. Vacuoles are cavities in the cytoplasm filled with cell sap- an aqueous solution of carbohydrates, organic acids, salts, low molecular weight proteins, pigments.

The concentration of substances in cell sap and in the external environment (soil, water bodies) are usually not the same. If the intracellular concentration of substances is higher than in the external environment, water from the environment will enter the cell, more precisely into the vacuole, at a faster rate than in the opposite direction. With an increase in the volume of cell sap, due to the entry of water into the cell, its pressure on the cytoplasm, which fits tightly to the membrane, increases. When a cell is completely saturated with water, it has its maximum volume. The state of internal tension of the cell, due to the high water content and the developing pressure of the cell contents on its membrane, is called turgor Turgor ensures that organs retain their shape (for example, leaves, non-lignified stems) and position in space, as well as their resistance to the action of mechanical factors. Loss of water is associated with a decrease in turgor and wilting.

If the cell is in hypertonic solution, the concentration of which is greater than the concentration of cell sap, then the rate of diffusion of water from the cell sap will exceed the rate of diffusion of water into the cell from the surrounding solution. Due to the release of water from the cell, the volume of cell sap is reduced and turgor decreases. A decrease in the volume of the cell vacuole is accompanied by the separation of the cytoplasm from the membrane - occurs plasmolysis.

During plasmolysis, the shape of the plasmolyzed protoplast changes. Initially, the protoplast lags behind the cell wall only in certain places, most often in the corners. Plasmolysis of this form is called corner(Fig. 1, B).

Then the protoplast continues to lag behind the cell walls, maintaining contact with them in certain places; the surface of the protoplast between these points has a concave shape. At this stage plasmolysis is called concave(Fig. 1, B).

Gradually, the protoplast breaks away from the cell walls over the entire surface and takes on a rounded shape. This plasmolysis is called convex.

If the protoplast retains its connection with the cell wall in certain places, then with a further decrease in volume during plasmolysis the protoplast acquires irregular shape. The protoplast remains connected to the shell by numerous Hecht's threads. This plasmolysis is called convulsive.

If a plasmolyzed cell is placed in hypotonic solution, the concentration of which is less than the concentration of cell sap, water from the surrounding solution will enter the vacuole. As a result of an increase in the volume of the vacuole, the pressure of the cell sap on the cytoplasm will increase, which begins to approach the cell walls until it takes its original position - it will happen deplasmolysis.

Osmosis. plays an important role both in the entry of gases and liquids into the plant and in their release - for example. during the absorption of soil solutions by roots, during the exchange of gases by leaves, etc. Likewise, oxygen is essential during the movement of nutrients within a plant from cell to cell. Osmotic movements are generally determined by the properties of cell membranes and mainly the peripheral (leathery) layer of protoplasm. The osmotic pressure exerted by the cell sap on this layer of protoplasm and on the membrane is usually quite significant; it is called cell turgor and is one of the necessary conditions for cell growth. Exosmosis weakens or completely destroys turgor, as a result of which the cell. Sucking force- the amount of excess of osmotic pressure inside the cell over the turgor pressure of the tense cell membrane. The greater the difference between them, the greater the suction force, which ensures that nutrients from water or soil solutions enter the cell. Lithophytic algae have the greatest sucking force - more than 150 atm, haloxerophytic subshrubs - up to 100 atm, hydrophytes have the least - 1-5 atm

35..VITAMINS, FAT SOLUBLE. Vitamin A (antixerophthalic).Vitamin D (antirachitic).Vitamin E (vitamin of reproduction).Vitamin K (antihemorrhagic).Vitamin A - retinol. Many people know that the main importance of this vitamin is its benefits for our vision. Also, it is involved in the regulation of hormone levels, affects the condition of the mucous membranes, stimulates regeneration processes in the skin, and ensures normal functioning nervous system. This vitamin is necessary for the beauty and health of women. Vitamins of group D. Ensure healthy teeth, bones, good resistance to diseases, etc. The group includes vitamins D1, D2, D3, D4, D5. Vitamin D3 stands out among them. Vitamin E is tocopherol. It affects tissue regeneration, circulation and blood clotting, protects cells from free radicals, helps the formation of collagen and elastic fibers. This vitamin is considered female. Its special significance for women is to help with premenstrual syndrome. Vitamin K. The main importance of this vitamin is to ensure normal blood clotting. It stimulates the production of prothrombin. This is a group of vitamins that includes several types of vitamin K.

36.cytoplasm, its chemical composition. Cytoplasm is colorless, has a mucous consistency and contains various substances, including high-molecular compounds, for example proteins, the presence of which determines the colloidal properties of the cytoplasm. Cytoplasm is part of the protoplast, enclosed between the plasmalemma and the nucleus. The basis of the cytoplasm is its matrix, or hyaloplasm, a complex colorless, optically transparent colloidal system capable of reversible transitions from sol to gel.

In the cytoplasm of plant cells there are organelles: small bodies that perform special functions - plastids, Golgi complex, endoplasmic reticulum, mitochondria, etc. Most of the processes of cellular metabolism take place in the cytoplasm, excluding synthesis nucleic acids, occurring in the nucleus. The cytoplasm is penetrated by membranes - the thinnest (4-10 nm) films, built mainly from phospholipids and lipoproteins. Membranes limit the cytoplasm from the cell membrane and vacuole and inside the cytoplasm form the endoplasmic reticulum (reticulum) - a system of small vacuoles and tubules connected to each other.

The most important property of the cytoplasm, associated primarily with the physicochemical properties of the hyaloplasm, is its ability to move. In cells with one large vacuole, movement is usually carried out in one direction (cyclosis) due to special organelles - microfilaments, which are filaments of a special protein - actin. The moving hyaloplasm entrains plastids and mitochondria. Cell sap, located in vacuoles, is an aqueous solution of various substances: proteins, carbohydrates, pigments, organic acids, salts, alkaloids, etc. The concentration of substances found in cell sap is usually higher than the concentration of substances in the external environment (soil, water bodies). The difference in concentrations to a certain extent determines the possibility of water and soil solutions entering the cell, which is to some extent explained by the phenomenon of osmosis. In a cell, the role of a semi-permeable membrane is played by the cytoplasm. The boundary layers of the cytoplasm lining the cell membrane and the cell vacuole are permeable only to water and some solutions, but impermeable to many substances dissolved in water. This property of the cytoplasm is called semi-permeability or selective permeability. Unlike the cytoplasm, the cell membrane is permeable to all solutions; it is impenetrable only to solid particles. The entry of substances into the cell cannot be reduced only to osmotic phenomena, which are expressed in adult cells with well-developed vacuoles. In reality, this is a very complex process due to many factors. The entire system of cytoplasmic colloids takes an active part in the absorption of substances. The intensity of movement depends on temperature, degree of lighting, oxygen supply, etc.

In very young cells, the cytoplasm fills almost the entire cavity. As the cell grows, small vacuoles appear in the cytoplasm filled with cell sap, which is an aqueous solution of various organic substances. Subsequently, with further cell growth, the vacuoles increase in size and, merging, often form one large central vacuole, pushing the cytoplasm towards the cell membrane. In such cells, all organelles are located in a thin wall layer of cytoplasm. Sometimes the nucleus remains in the center of the cell. In this case, the cytoplasm, forming a nuclear pocket around it, is connected to the wall layer by thin cytoplasmic strands.

The cytoplasm layer contains chloroplasts that line upper wall. They are almost round or slightly oval bodies. Occasionally you can see plastids pulled in the middle.

45. Isoenzymes, or isoenzymes, are isoforms or isotypes of the same enzyme that differ in amino acid sequence, existing in the same organism, but, as a rule, in different cells, tissues or organs. Isoenzymes are usually highly homologous in amino acid sequence and/or similar in spatial configuration. The active centers of isoenzyme molecules are especially conservative in maintaining their structure. All isoenzymes of the same enzyme perform the same catalytic function, but can differ significantly in the degree of catalytic activity, regulatory features, or other properties. An example of an enzyme that has isoenzymes is hexokinase, which has four isotypes, designated by Roman numerals from I to IV. Moreover, one of the isotypes of hexokinase, namely hexokinase IV, is expressed almost exclusively in the liver and has special physiological properties, in particular, its activity is not inhibited by its reaction product glucose-6-phosphate. Another example of an enzyme that has isoenzymes is pancreatic amylase amylase differs in amino acid sequence and properties from the amylase of the salivary glands, intestines and other organs. This served as the basis for the development and application of a more reliable method for diagnosing acute pancreatitis by determining not total plasma amylase, but pancreatic isoamylase. The third example of an enzyme that has isoenzymes is creatine phosphokinase - the isotype of this enzyme expressed in the heart differs in amino acid sequence from creatine phosphokinase skeletal muscles. This makes it possible to differentiate myocardial damage (for example, during myocardial infarction) from other causes of increased CPK activity by determining the myocardial isotype of CPK in the blood

Many solutions enter the cell osmotically. Osmosis (from the Greek osmos - pressure) is the one-way penetration of water through a semi-permeable shell. It can be observed if two solutions of different concentrations are separated by a semi-permeable partition that is accessible to water, but does not allow the dissolved substance to pass through. Water with a certain force, depending on the difference in concentration, will be attracted by a more saturated solution from a more dilute one. The resulting pressure on the semipermeable membrane is called osmotic pressure. The study of the osmotic properties of cells began with the great Dutch botanist G. de Vries (1848-1935), who discovered turgor in plants. De Vries' experiments, according to Van Hoff, formed the basis for the theory of osmotic pressure developed by this famous physicist.

Animal and plant cells contain solutions of salts and other osmotically active substances (sugars, urea). This determines a certain osmotic pressure. In the cells of terrestrial animals it is about 8 atm; in marine invertebrates it increases to 38 atm. Plant cells usually have an osmotic pressure of 5 to 20 atm, but in some cases it can reach 100 or even 140 atm. Here the conditions of existence are of primary importance, not the systematic position. Representatives of the same species growing in different conditions have different osmotic pressure of cell sap.

Solutions in which the osmotic pressure is the same as in the cells are called isotonic. When cells are immersed in isotonic solutions, their volume remains unchanged. Isotonic salt solutions are called physiological. For different objects, the concentration of table salt in physiological solution is not the same. Thus, for animals from the class of amphibians it is equal to a 0.75% NaCl solution, for mammals - 0.9%, for insects - 1%, and for marine invertebrates it corresponds to a salt concentration of sea ​​water- 3% NaCl. Saline solutions and other isotonic liquids are used in medicine. They are used for severe dehydration and blood loss in patients.

A solution whose osmotic pressure is higher than that in the cells is called hypertonic. Plant cells immersed in such a solution begin to lose water, the protoplasm of the cell shrinks and peels off from the shell. This phenomenon is called plasmolysis (Figure 20). When osmotic pressure decreases in plant cells, turgor decreases. Turgor refers to the tense state of cell membranes caused by pressure on them from the inside. A plant whose cells have reduced turgor becomes flabby. This phenomenon can be easily observed in plucked and withering plants and their fruits. In some diseases, such as cholera, as a result of severe dehydration of the patient's cells, his entire body becomes flabby and the skin becomes “doughy.”

In surgery, a hypertonic solution of steamed salt is widely used in the treatment of infected wounds. A gauze bandage moistened with a Hypertonic solution absorbs pus well, which promotes wound healing.

The opposite of plasmolysis is observed when plant cells are immersed in a hypotonic solution. In this solution the osmotic pressure is lower than in the cells. Water begins to rush into the cell, the cell swells, the pressure on the membranes becomes greater, and turgor increases. If there is a significant difference in osmotic pressure, the cell may burst.

Isolated animal cells in hypotonic solutions are destroyed. The same thing will happen to red blood cells if a hypotonic solution is introduced into the blood of a person or animal. They first swell, and then their outer membrane ruptures (Fig. 21).

The outer layer of the cell, i.e. its membrane, allows not only water to pass through, but also, to some extent, substances dissolved in it. A living cell actively regulates osmotic pressure by changing the concentrations of osmotically active substances. Single-celled animals living in fresh water have developed special devices (pulsating vacuoles) that remove excess water from cells. Single-celled organisms that do not have pulsating vacuoles remove excess water through the cell membrane. In higher animals, osmotic pressure in the whole organism is regulated by the system of excretory organs (kidneys).

A plant cell differs from an animal cell mainly in the structure of the cell membrane, the presence of chloroplasts that provide photosynthesis and vacuoles filled with cell sap (Fig. 2-13).

Cell membrane consists of two layers. The inner layer is adjacent to the cytoplasm and is called the cytoplasmic or plasma membrane, over which an outer thick layer of cellulose is formed, called the cell wall. The cell membrane is easily permeable to liquids and gases, and is penetrated by the thinnest tubules (plasmodesmata) connecting neighboring cells.

o Plasmodesmata are pores through which substances are exchanged between neighboring cells and cells are organized into a single whole. An analogue of gap intercellular junctions between animal cells.

Plastids (chloroplasts)- double-membrane formations with their own DNA; presumably arose from cyanobacteria as a result of fusion with a plant cell. They provide photosynthesis of ATP and organic compounds with the participation of solar energy.

The vacuole is a single-membrane sac-like structure filled with cell sap that takes part in maintaining osmotic homeostasis and cell shape. Vacuoles develop from cisterns of the endoplasmic reticulum. The membrane that encloses the vacuole is called the tonoplast. In a young plant cell, cell sap accumulates in small vacuoles; in an adult cell, the vacuoles merge, the nucleus and other organelles move to the periphery, and the vacuole occupies almost the entire volume of the cell. The composition of the cell sap includes water in which organic acids (oxalic, malic, citric, etc.), sugars (glucose, sucrose, fructose), and mineral salts (calcium nitrate, magnesium sulfate, potassium phosphate, iron salts) are dissolved. One of the important functions of vacuoles is the accumulation of ions and maintenance of turgor (turgor pressure).

Rice. 2-13. The structure of a plant cell. 1 - Golgi complex; 2 - freely located ribosomes; 3 - chloroplasts; 4 - intercellular spaces; 5 - polyribosomes (several ribosomes interconnected); 6 - mitochondria; 7 - lysosomes; 8 - granular endoplasmic reticulum; 9 - smooth endoplasmic reticulum; 10 - microtubules; 11 - plasmodesmata; 12 - cell membrane; 13 - nucleolus; 14 - nuclear membrane; 15 - pores in the nuclear envelope; 16 - cellulose shell; 17 - hyaloplasm; 18 - tonoplast; 19 - vacuole; 20 - core.

2. Osmotic properties of a plant cell

1. Place fragments of the leaves of the aquatic Vallisneria plant on a glass slide and apply a few drops of distilled water so that the Vallisneria leaves remain in the aqueous environment. Cover the object with a cover glass and examine the turgor state of the cells under a microscope. At high magnification of the microscope, rectangular cells are visible, having a colorless double-contour shell and adjacent protoplasm with green chloroplasts (Fig. 2-14).

2. Replace the water in which the plant cells are located with a hypertonic solution (8% sodium chloride). To do this, use filter paper to absorb water. from under the cover glass. Then, using a pipette, drop a hypertonic solution under the coverslip. In a hypertonic solution, cells lose water and move from a turgor state to a state of plasmolysis. The preparation shows cells in which, as a result of loss of water from the vacuoles, the protoplasm with chloroplasts is separated from the cell membrane. The contents of the cell are compressed.

3. Next, you should again replace the hypertonic solution with distilled water using the above method. When the solution is replaced, the cells are saturated with water and return to their previous turgor state, which after plasmolysis is called deplasmolysis.

Rice. 2-14. Movement of water through the cell wall of a plant cell. A - turgor; B -

plasmolysis; B - deplasmolysis.

Content

10. Osmotic properties of the cell. Turgor. Plasmolysis and deplasmolysis

Osmotic call the phenomena occurring in a system consisting of two solutions separated by a semi-permeable membrane. In a plant cell, the role of semi-permeable films is performed by the boundary layers of the cytoplasm: plasmalemma and tonoplast.
Plasmalemma- the outer membrane of the cytoplasm adjacent to the cell membrane. Tonoplast- inner cytoplasmic membrane surrounding the vacuole. Vacuoles are cavities in the cytoplasm filled with cell sap- an aqueous solution of carbohydrates, organic acids, salts, low molecular weight proteins, pigments.
The concentration of substances in cell sap and in the external environment (soil, water bodies) are usually not the same. If the intracellular concentration of substances is higher than in the external environment, water from the environment will enter the cell, more precisely into the vacuole, at a faster rate than in the opposite direction. With an increase in the volume of cell sap, due to the entry of water into the cell, its pressure on the cytoplasm, which fits tightly to the membrane, increases. When a cell is completely saturated with water, it has its maximum volume. The state of internal tension of the cell, due to the high water content and the developing pressure of the cell contents on its membrane, is called turgor(Fig. 1, A) . Turgor ensures that organs retain their shape (for example, leaves, non-lignified stems) and position in space, as well as their resistance to the action of mechanical factors. Loss of water is associated with a decrease in turgor and wilting.
If the cell is in hypertonic solution, the concentration of which is greater than the concentration of cell sap, then the rate of diffusion of water from the cell sap will exceed the rate of diffusion of water into the cell from the surrounding solution. Due to the release of water from the cell, the volume of cell sap is reduced and turgor decreases. A decrease in the volume of the cell vacuole is accompanied by the separation of the cytoplasm from the membrane - occurs plasmolysis.
During plasmolysis, the shape of the plasmolyzed protoplast changes. Initially, the protoplast lags behind the cell wall only in certain places, most often in the corners. Plasmolysis of this form is called corner(Fig. 1, B).
Then the protoplast continues to lag behind the cell walls, maintaining contact with them in certain places; the surface of the protoplast between these points has a concave shape. At this stage plasmolysis is called concave(Fig. 1, B).
Gradually, the protoplast breaks away from the cell walls over the entire surface and takes on a rounded shape. This plasmolysis is called convex(Fig. 1, D).
If the protoplast retains its connection with the cell wall in certain places, then with a further decrease in volume during plasmolysis, the protoplast acquires an irregular shape. The protoplast remains connected to the shell by numerous Hecht's threads. This plasmolysis is called convulsive(Fig. 1, D).
If a plasmolyzed cell is placed in hypotonic solution, the concentration of which is less than the concentration of cell sap, water from the surrounding solution will enter the vacuole. As a result of an increase in the volume of the vacuole, the pressure of the cell sap on the cytoplasm will increase, which begins to approach the cell walls until it takes its original position - it will happen deplasmolysis.

Rice. 1. Plasmolysis of a plant cell:
A - cell in a state of turgor; B - corner; B - concave; G - convex; D - convulsive.
1 - shell, 2 - vacuole, 3 - cytoplasm, 4 - nucleus, 5 - Hecht filaments.

17. Describe the substances produced by the protoplast of a plant cell: vitamins, hormones, enzymes, phytoncides, essential oils, antibiotics, tannins and their use in national economy

Protoplast is the active content of a plant cell. The main component of protoplast is protein . The cell membrane and vacuole are waste products protoplast.
Vitamins- substances that are very complex in structure and physiological activity, which are extremely necessary for the normal functioning of plants. Vitamins control the general course of metabolism in plants.
Application. A large number of plants serve as the main suppliers of vitamins contained in veterinary drugs and feed additives.
Hormones - physiologically active substances that regulate the processes of growth and development. Phytohormones - low molecular weight organic substances , produced by plants and having regulatory functions. Phytohormones cause various physiological and morphological changes in plant parts sensitive to their action. Phytohormones have a wide spectrum of action. Phytohormones regulate many life processes of plants: seed germination, growth, differentiation of tissues and organs, flowering, fruit ripening, etc. Formed in one organ (or part thereof) of the plant, phytohormones are usually transported to another (or part thereof). There is a generally accepted classification in which among plant hormones there are 5 main groups of classical hormones. Hormones from different plants may differ in chemical structure, so they are grouped based on their effect onplant physiologyand general chemical structure.
Let us give several examples of the use of phytohormones in the national economy. Synthetic auxins are used to enhance root formation in cuttings that otherwise do not root well; for producing parthenocarpic fruits, for example, in tomatoes in greenhouses, where conditions make pollination difficult, etc. In high concentrations, synthetic auxins are used as herbicides to control certain weeds. An important property of cytokinins is their ability to slow down aging, which is especially valuable for green leafy vegetables. Under the influence of some synthetic phytohormones created in the last half century, plant internodes are shortened, stems become stiffer, and leaves acquire a dark green color. Plant resistance to drought, cold and air pollution increases.
Plant enzymes. Enzymes (enzymes) are complex substances of protein nature and are biological catalysts, the presence of which is necessary to excite and accelerate biochemical reactions occurring in the cell. The most important life processes - respiration, assimilation, synthesis and breakdown of proteins, etc. - can only be carried out under the influence of certain enzymes. Enzymes differ from inorganic catalysts by their high specificity, i.e., the action of one enzyme is strictly limited to one substance or a group of related substances.
Currently, over 800 different enzymes are known, which, according to the nature of their action, are divided into 2 main groups - hydrolytic and desmolytic enzymes. Hydrolytic enzymes include all enzymes that cause the hydrolysis of sugars, fats, glycosides and other organic substances. Demolytic enzymes cause the bond between carbon atoms to break, which releases large amounts of thermal energy. Demolytic enzymes provide such important life processes as respiration (peroxidases, catalases), fermentation and many others.
Application. It should be noted that most enzymes that have important in industry and agriculture, refer to enzymes that act as catalysts in the breakdown or “hydrolysis” of large organic molecules such as starch, cellulose and protein. These enzymes actually attack complex molecules, speeding up the process of breaking them down into simpler substances. These enzymes are called hydrolytic or hydrolases.
Phytoncides- formed plants biologically active substances, killing or suppressing growth and development bacteria , microscopic mushrooms, protozoa . Typical representatives of phytoncides are essential oils , extracted from plant raw materials by industrial methods . Phytoncides are all secreted by plants. fractions of volatile substances , including those that are practically impossible to collect in appreciable quantities. These phytoncides are also called “native antimicrobial substances of plants.” Chemical the nature of phytoncides is not essential for their functions , it could be a complex of compounds - glycosides, terpenoids, tanning agents etc., so-called secondary metabolites.
Native phytoncides play an important role in immunity plants and in relationships organisms in biogeocenoses . The release of a number of phytoncides increases when plants are damaged. Volatile phytoncides are capable of exerting their effects at a distance, for example leaf phytoncides oak, eucalyptus, pine and many others. The strength and spectrum of antimicrobial action of phytoncides are very diverse. Phytoncides garlic, onion, horseradish, red pepper kill many types of protozoa, bacteria and lower fungi in the first minutes and even seconds. Volatile phytoncides destroy protozoa ( ciliates), many insects in a short time (hours or minutes ). Phytoncides are one of the factors in the natural immunity of plants (plants sterilize themselves with the products of their vital activity). The protective role of phytoncides is manifested not only in the destruction of microorganisms, but also in the suppression of them reproduction , in the negative chemotaxis of motile forms microorganisms, in stimulating the vital activity of microorganisms that are antagonists of pathogenic forms for a given plant, in repelling insects, etc.
Let us give several examples of the use of phytoncides in the national economy. Phytoncides are also used for storing fruits, vegetables, and fruit and vegetable juices. When grated horseradish gruel is placed in a hermetically sealed vessel with fruits or berries, they can be stored for several months. Mustard phytoncide, allylic oil, also has high activity. If you add 25 mg of this oil per liter of grape juice, the juice retains its properties for a long time and does not spoil. Phytoncides have a significant impact on the life of plants. For example, ethylene gas released by some fruits stimulates the ripening of tomato, lemon, orange and other plants and increases leaf fall, and phytoncides from wild garlic bulbs have an inhibitory effect on the growth and development of neighboring plants.
Essential oils, mostly liquid, volatile, strongly odorous and acrid, burning taste, bodies of various compositions; found especially in those plant families that have a strong odor. Contained mainly in flowers, seeds and fruits. Essential oils are used primarily for flavoring food products, drinks, household chemicals, in the pharmaceutical industry, in medicine and aromatherapy , and also as solvents (turpentine). The most widely used arecitrus essential oils, peppermint essential oil and turpentines obtained from coniferous trees.
Antibiotic - a substance capable of inhibiting the growth of microorganisms or causing their death. Antibiotics of plant origin are called phytoncides (see above). These are chloreline, tomatine, sativine, obtained from garlic, and aline, isolated from onions. Antibiotics are widely used in veterinary practice to combat a number of plant diseases (pears, beans and peppers) and to purify viral preparations. Farmers add antibiotics to feed to speed up the growth of poultry, pigs and cows.
Tannins - astringents of plant origin. In plants (bark, wood, roots, leaves, fruits) they appear either as normal products of their vital activity (physiological tannins), or they constitute (pathological tannins) a more or less significant part of the painful growths that form on leaves and other organs some types of oak and sumac due to the sting produced by insects. Tannins are mostly amorphous, have a more or less clearly expressed acidic character and have the remarkable property (mainly physiological tannins) of tanning leather (hides), that is, taking away their ability to rot and harden to a large extent when dry. Herbs with a high content of tannins are used as a gargle for sore throats and gum inflammation, but primarily as a remedy against diarrhea.

44. Anatomical structure of the stems of herbaceous plants from the class of dicotyledons and monocotyledons. Provide drawings

1. Structure of the stem of dicotyledonous plants

At the stem, as well as at the root, below the growth cone in the zone of the embryonic leaves, differentiation of the cells of the primary meristem occurs and the primary structure is formed. In gymnosperms and most dicotyledonous angiosperms, this is followed by the appearance of a lateral meristem - the cambium, in the form of a continuous cambial cylinder, forming secondary conducting tissues and thus causing the growth of the stem in thickness. The origin of the cambium in herbaceous dicotyledonous plants can be different. In some plants it arises very early from a continuous ring of procambium, following the appearance of the primary elements of xylem and phloem. In this case, a non-tufted stem structure is formed. In other plants, the procambium is formed by cords and the cambium arises not only from the procambium, but also from the parenchyma between already formed vascular bundles. In this case, either bunched or transitional structure of the stem.
Bundle structure will occur if the interfascicular cambium differentiates only into parenchyma. The bunches are located at the same distance from the surface of the stem. Bundles in dicotyledons are either private or general. As long as a tuft follows down the stem without merging with other tufts, it is called a private or leaf trail. These bundles are separated from neighboring bundles by parenchymal tissue. When private bundles come into contact with each other, the boundaries between them disappear and a common bundle is formed.
Transitional structure is formed if the interfascicular cambium, like the fascicular cambium, forms the histological elements of phloem and xylem. Only a few herbaceous dicotyledons do not form a continuous cambial cylinder, and the cambium is located only inside the bundles, between which the parenchyma is located. In such plants, the stem cannot thicken much.
In herbaceous dicotyledonous plants, the primary bark is distinguished And modified central cylinder (stele) . Their phellogen is either poorly developed or absent. The primary cortex changes little during development, only becoming thinner as a result of stretching. The central cylinder includes tissues arising from the pericycle, remnants of primary phloem and secondary phloem, cambium, secondary and remnants of primary xylem and pith. Mechanical tissues are reduced.

Longitudinal and transverse sections of the stem of a dicotyledonous plant.
1 - apical meristem zone, 2 - leaf primordia, 3 - educational ring, 4 - pith, 5 - procambium, 6 - primary cortex, 7 - primary phloem, 8 - primary xylem, 9 - cambium, 10 - epidermis, 11 - pericycle , 12 - endoderm, 13 - secondary phloem, 14 - secondary xylem, 15 - parenchyma of the primary cortex, 16 - collenchyma, 17 - leaf trail.

2. Structure of the stem of monocots

Monocots have primary bundle structure. In this case, the bunches are distributed throughout the entire cross-section of the stem, as if randomly. This arrangement of bunches, called palm, arises due to the fact that they are all leaf traces, and when passing along the internode they bend. All bundles in a monocot stem are private. Each bundle is surrounded by a layer of mechanical tissue, so when the bundles come together, complete fusion does not occur.
The most common are two types of bundle structure of the stem: with a well-defined primary cortex and with the absence of distinct boundaries between the primary cortex and the central cylinder. In the stem of most monocots, as well as in the root, a cambium is not formed, so it does not have a secondary thickening. Mechanical strength is provided by sclerified epidermis and parenchyma.
The herbaceous stem can be hollow or fulfilled.

The structure of a hollow stem (straw) In cereals, sclerenchyma forms a continuous ring with projections closely adjacent to the epidermis. Between the projections there are areas of thin-walled chlorenchyma. Over time, the walls of the chlorenchyma and epidermis become lignified. The conducting bundles are arranged in a checkerboard pattern. The outer circle bundles are adjacent to the sclerenchyma, and the inner ones are located among the parenchyma cells.
The most typical stem is a straw in rye, oats, and wheat. Corn has a complete stalk, so the vascular bundles are more or less scattered across the cross section. In sorghum and millet, the bundles are shifted to the periphery due to the formation of a relatively small central air cavity.

Rice. Straw

The structure of the completed stem. The structure of the completed stem can be seen using the example of the iris stem. Under the epidermis there is chlorenchyma. This is followed by a single-celled layer of endoderm, transformed into a starch-bearing vagina. This is the inner boundary of the primary cortex. Sclerenchyma of pericyclic origin is closely adjacent to the endodermis. The core occupies most of the stem. It consists of parenchyma and collateral closed bundles.

69. Pistil, concept of carpel. Types of ovary by position and number of nests. Provide drawings

Pistil - female reproductive organflowering plants, located in the center flower
Each pistil has three distinct parts, namely:

lower swollen - ovary , called by some authors the ovary;
column , constituting a direct continuation of the ovary,
stigma , ending with a column.

The ovary contains one or more ovule , formerly called testicles. These are very small, sometimes barely noticeable bodies that are exposed to fertilization and then turning into seeds.
The style, which in many plants is not developed at all or is very poorly developed, contains inside a canal lined with delicate and loose tissue, which often completely fulfills it. Fertilization occurs through it.
The stigma is lined, like the channel of the style, with the same loose tissue, which oozes out thick sugary moisture and receives fertile dust.
Carpel, an organ in the flower of angiosperms on which the ovules (ovules) develop. A pistil is formed from 1 or several carpels; the collection of carpels is called gynoecium . The carpel is considered an organ of leaf origin, homologous, however, not to the leaf, but megasporophyll.
The ovary is the most essential part pistil, bearing ovules . Depending on the position of the ovary in relation to other parts of the flower, the upper, semi-inferior and lower ovaries are distinguished. The superior ovary is evolutionarily more primitive, and the inferior ovary in one way or another arose from the superior one.
The upper (free) ovary is attached by its base to the receptacle, not fused with it or with other parts of the flower. The lower ovary is located under the flower, the remaining parts of the flower are attached to its apex.
The semi-inferior ovary fuses with the receptacle or with the bases of the remaining parts of the flower, not to the very top.

1 - top , 2 - semi-inferior , 3 - lower , 4 - upper, surrounded by walls hypanthia .

84. Methods of dispersal of fruits and seeds. Give examples. Biological role of fruit and seed dispersal

At the beginning of the 20th century. Swedish botanist R. Sernander gave any parts of plants with the help of which they are able to disperse the general name diaspores. The main types of diasporas inseed plants- fruits and seeds.
There are two main ways in which diasporas spread. One - through mechanisms developed in the process of evolution by the plant itself, the other - with the help of various external agents - wind, water, animals, humans, etc. The first type was called autochories, the second - allochory.
The plants are called accordingly autochores and allochores.
The fruits and seeds of autochoirs are dispersed relatively close to the mother plant, usually no more than a few meters from it. The group of autochorous plants is divided into mechanochores and barochores.
The fruits of many mechanochores are opened through nests or valves, and seeds spill out of them. This is the case withviolets tricolor, types of tulip etc. Some mechanochores actively scatter seeds thanks to special adaptations in the fruits, which are based on the increased osmotic pressure of the cells of the main tissue. The most common plants of this kind areimpatiens vulgare, springy ecbalium, or mad cucumber. The fruits of some clovers that have fallen to the ground can “crawl” over short distances due to the hygroscopic movements of the teeth calyxes attached to the fruit.
To the barochors include plants with heavy fruits and seeds. These include oak acorns, walnut fruits, seeds horse chestnut. These seeds fall from the mother plant and end up in close proximity to their parents.
To the autochoir group also applygeocarp plants. In geocarpous species, the fruits during development are embedded in the soil and ripen there. The most famous of themunderground peanuts, or groundnuts.
There are four main ways allochory. These are anemochory, zoochory, hydrochory and anthropochory.
Anemochore seeds carried by air movement. The indehiscent fruits of anemochores are characterized by a variety of flying devices: flies, lionfish, etc. A classic example of plants with flying fruits is dandelion . Its fruits are capable of flying through the air over considerable distances. winged fruitcommon ash And sycamore maple, having detached themselves from the mother plant, they can glide several tens of meters. The wing that emerged from bracts and bearing a whole inflorescence, species of linden have.
Adaptations for anemochorous widespread not only fruits, but also seeds . In this case, the fruits containing such seeds are necessarily opened, and the spilled seeds are carried by the wind. Everyone is familiar with poplar fluff, which is the pubescence of small seeds. poplars and easily blows them away even in light winds.
In some cases, a dead plant with mature fruits is capable of moving on its own under gusts of wind. This group of plants is called tumbleweed. The drying stem of such plants easily breaks off, and the loose or more or less compact light bush is freely driven by the wind, scattering the ripening seeds. Tumbleweed plants include many steppe inhabitants from a wide variety of taxonomic groups, e.g.swing the plump one, Solyanka kholmovaya and etc.
Fruits of hydrochores , spreading with the help of water, are equipped with a dense, low-permeable water endocarp , fibrous lung
etc.................