plant stomata

found in their skin (epidermis). Each plant is in constant exchange with the surrounding atmosphere. It constantly absorbs oxygen and releases carbon dioxide. In addition, with its green parts, it absorbs carbon dioxide and releases oxygen. Then, the plant constantly evaporates water. Since the cuticle, which covers the leaves and young stems, very weakly passes gases and water vapor through itself, there are special holes in the skin for unhindered exchange with the surrounding atmosphere, called U. On the transverse section of the leaf (Fig. 1), U. appears in slit ( S) leading to the air cavity ( i).

Fig. 1. Stoma ( S) of a hyacinth leaf in section.

On both sides of the U. there is one closing cell. The shells of the guard cells give two outgrowths towards the stomatal opening, due to which it breaks up into two chambers: the anterior and posterior courtyard. When viewed from the surface, U. appears as an oblong slit surrounded by two semilunar guard cells (Fig. 2).

During the day, U. are open, but at night they are closed. U. are also closed during the day during a drought. U.'s closing is made by guard cells. If a piece of the skin of the leaf is put into water, then the U. continues to remain open. If the water is replaced with a sugar solution that causes cell plasmolysis, then the U. will close. Since the plasmolysis of cells is accompanied by a decrease in their volume, it follows that the closure of cells is the result of a decrease in the volume of guard cells. During drought, the guard cells lose part of their water, decrease in volume and close the U. The leaf is covered with a continuous layer of cuticle, which is poorly permeable to water vapor, which prevents further drying. Night closing U. is explained by the following considerations. Guard cells constantly contain chlorophyll grains and are therefore capable of assimilating atmospheric carbon dioxide, i.e., of self-feeding. Organic substances accumulated in the light strongly attract water from the surrounding cells, so the guard cells increase in volume and open. At night, the organic substances produced in the light are consumed, and with them the ability to attract water is lost, and U. closes. U. are both on the leaves and on the stems. On leaves, they are placed either on both surfaces, or on one of them. grassy, soft leaves have U. both on the upper and on the lower surface. Hard leathery leaves have U. almost exclusively on the lower surface. In leaves floating on the surface of the water, U. are exclusively on the upper side. The amount of U. in different plants is very different. For most leaves, the number of U. per square millimeter fluctuates between 40 and 300. Largest number U. is located on the lower surface of the Brassica Rapa leaf - per 1 sq. mm 716. There is some relationship between the amount of U. and the humidity of the place. AT general plants wet areas have more U. than plants in dry areas. In addition to ordinary U., which serve for gas exchange, many plants also have water U. They serve to release water not in a gaseous state, but in a liquid state. Instead of an air cavity lying under ordinary U., under water U. there is a special aquifer tissue consisting of cells with thin membranes. Water U. are found for the most part in plants of damp areas and are found on various parts leaves, regardless of the ordinary U., which are located right there. Water U. emit drops of water for the most part when, due to the high humidity of the air, air-bearing U. can not evaporate water. All such formations are called hydathod(Hydathode). An example is the hydathodes of Gonocaryum pyriforme (Fig. 3).

A cross-section through a leaf shows that some of the skin cells have changed in a special way and turned into hydathodes. Each hydathode consists of three parts. A slanting outgrowth protrudes outward, pierced by a narrow tubule through which the water of the hydathode flows. The middle part looks like a funnel with very thickened walls. The lower part of the hydathode consists of a thin-walled bubble. Some plants give off their leaves large quantities water, without having any specially arranged hydathods. Eg. different kinds Salacia secrete such large quantities of water between 6-7 o'clock in the morning that they fully deserve the name rain shrubs: with a light touch on the branches, real rain falls from them. Water is released by simple pores covering the in large numbers outer membranes of skin cells.

V. Palladin.

encyclopedic Dictionary F. Brockhaus and I.A. Efron. - St. Petersburg: Brockhaus-Efron. 1890-1907 .

See what "Plant stomata" is in other dictionaries:

They are found in their skin (epidermis). Each plant is in constant exchange with the surrounding atmosphere. It constantly absorbs oxygen and releases carbon dioxide. In addition, with its green parts, it absorbs carbon dioxide and releases oxygen ...

Stomata of a tomato leaf under an electron microscope Stomata (Latin stoma, from Greek στόμα “mouth, mouth”) in botany is a pore located on the lower or upper layer of the epidermis of a plant leaf, through which water evaporates and gas exchange with ... ... Wikipedia

The first attempts to classify flowering plants, like flora in general, were based on a few, arbitrarily taken, easily conspicuous external signs. These were purely artificial classifications, in which in one ... ... Biological Encyclopedia

Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron

Groups of cells located in the body of a plant in a certain order, having a certain structure and serving for various vital functions of the plant organism. The cells of almost all multicellular plants are not homogeneous, but are collected in T. In the lower ... Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron- are such processes and phenomena occurring in a living plant organism that never occur during its normal life. According to Frank, B. plants is a deviation from the normal state of the species ... Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron

Contents: The subject of F.F. nutrition. F. growth. F. forms of plants. F. reproduction. Literature. Plant physics studies the processes that take place in plants. This part of the vast plant science of botany differs from its other parts of taxonomy, ... ... Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron

Leaf (folium), an organ of higher plants that performs the functions of photosynthesis and transpiration, as well as providing gas exchange with the air and participating in other processes. critical processes plant life. Morphology, leaf anatomy and its ... ... Great Soviet Encyclopedia

Scientists still cannot explain the mechanism that controls plant stomata. Today, we can only say with certainty that the dose of solar radiation is not an unambiguous and decisive factor influencing the closure and opening of stomata, writes PhysOrg.

To live, plants must take in carbon dioxide from the air for photosynthesis and draw water from the soil. They do both with the help of stomata - pores on the surface of the leaf, surrounded by guard cells, which these stomata open and close. Water evaporates through the pores and is maintained D.C. liquids from roots to leaves, but the plants regulate the level of evaporation so as not to dry out in hot weather. On the other hand, photosynthesis constantly requires carbon dioxide. Obviously, stomata sometimes have to solve almost mutually exclusive tasks: to prevent the plant from drying out and at the same time deliver air with carbon dioxide.

The method of regulating the work of stomata has long occupied science. The generally accepted point of view is that plants take into account the amount of solar radiation in the blue and red spectral ranges and, depending on this, keep their stomata open or closed. But not so long ago, several researchers proposed an alternative hypothesis: the state of the stomata depends on the total amount of absorbed radiation (and not just on its blue and red parts). Sunlight not only heats the air and the plant, it is essential for the photosynthesis reaction. Given the total dose of radiation, the stomata could more accurately respond to changes in light - and therefore more accurately control the evaporation of moisture.

Researchers from the University of Utah (USA), who put this theory to the test, were forced to admit that a revolution in plant physiology is not yet in sight. The conclusion that plants come from total radiation was based on temperature measurements on the leaf surface. Keith Mott and David Peak have found a way to determine the internal temperature of a leaf: according to scientists, it is the difference between the external and internal temperatures that determines the rate of evaporation. As the authors write in the journal PNAS, they failed to find a correlation between the temperature difference inside and on the surface of the leaf and the total radiation dose. It turns out that the stomata also ignored this total radiation.

According to the researchers, the most likely mechanism that controls the stomata would be something like a self-organizing network, vaguely reminiscent of a neural network (however crazy it may sound when applied to plants). Even the generally accepted hypothesis about the blue and red parts of the spectrum does not explain everything about the work of stomata. Is it possible in this connection to imagine that all guard cells are somehow connected with each other and can exchange certain signals? Being united, they could just quickly and accurately respond both to changes in the external environment and to the demands of the plant.

There are three types of reactions of the stomatal apparatus to environmental conditions:

1. hydropassive reaction- this is the closure of the stomatal fissures, caused by the fact that the surrounding parenchymal cells are overflowing with water and mechanically squeeze the guard cells. As a result of compression, the stomata cannot open and the stomatal gap does not form. Hydropassive movements are usually observed after heavy irrigation and can cause inhibition of the photosynthesis process.

2. Hydroactive reaction opening and closing are movements caused by a change in the water content of the guard cells of the stomata. The mechanism of these movements is discussed above.

3. photoactive reaction. Photoactive movements are manifested in the opening of stomata in the light and closing in the dark. Of particular importance are red and blue rays, which are most effective in the process of photosynthesis. This is of great adaptive importance, because due to the opening of stomata in the light, CO 2 diffuses to the chloroplasts, which is necessary for photosynthesis.

The mechanism of photoactive movements of stomata is not entirely clear. Light has an indirect effect through a change in the concentration of CO 2 in the guard cells of the stomata. If the concentration of CO 2 in the intercellular spaces falls below a certain value (this value depends on the plant species), the stomata open. When the concentration of CO 2 increases, the stomata close. In the guard cells of the stomata there are always chloroplasts and photosynthesis occurs. In the light, CO 2 is assimilated in the process of photosynthesis, its content decreases. According to the hypothesis of the Canadian physiologist W. Skars, CO 2 affects the degree of stomata openness through a change in pH in guard cells. A decrease in the content of CO 2 leads to an increase in the pH value (a shift to the alkaline side). On the contrary, darkness causes an increase in CO 2 (due to the fact that CO 2 is released during respiration and is not used in the process of photosynthesis) and a decrease in pH (shift to the acid side). Changing the pH value leads to a change in the activity of enzyme systems. In particular, a shift in the pH value to the alkaline side increases the activity of enzymes involved in the breakdown of starch, while a shift to the acid side increases the activity of enzymes involved in the synthesis of starch. The breakdown of starch into sugars causes an increase in the concentration of dissolved substances, in connection with this, the osmotic potential and, as a result, the water potential become more negative. In the guard cells, water begins to flow intensively from the surrounding parenchymal cells. The stomata open. The opposite changes occur when processes shift towards starch synthesis. However, this is not the only explanation. It was shown that the guard cells of the stomata contain significantly more potassium in the light compared to the dark. It has been established that the amount of potassium in the guard cells increases by 4-20 times when the stomata open, while this indicator decreases in the accompanying cells. There is a redistribution of potassium. When the stomata open, a significant gradient of the membrane potential arises between guard and accompanying cells (I.I. Gunar, L.A. Panichkin). The addition of ATP to the epidermis floating on the KC1 solution increases the rate of stomata opening in the light. An increase in the ATP content in the guard cells of the stomata during their opening was also shown (S.A. Kubichik). It can be assumed that ATP, formed during photosynthetic phosphorylation in guard cells, is used to enhance the intake of potassium. This is due to the activity of H + -ATPase. Activation of the H + -pump promotes the release of H + from guard cells. This leads to transport along the K+ electrical gradient into the cytoplasm and then into the vacuole. Increased intake of K +, in turn, promotes the transport of C1 - along the electrochemical gradient. Osmotic concentration increases. In other cases, the intake of K + is balanced not by C1 -, but by malic acid salts (malates), which are formed in the cell in response to a decrease in pH as a result of the release of H +. The accumulation of osmotically active substances in the vacuole (K + , C1 - , malates) reduces the osmotic, and then the water potential of the guard cells of the stomata. Water enters the vacuole and the stomata open. In the dark, K + is transported from a certain value (this value depends on the type of plant), the stomata open. When the concentration of CO 2 increases, the stomata close. In the guard cells of the stomata there are always chloroplasts and photosynthesis occurs. In the light, CO 2 is assimilated in the process of photosynthesis, its content decreases. According to the hypothesis of the Canadian physiologist W. Skars, CO 2 affects the degree of stomata openness through a change in pH in guard cells. A decrease in the content of CO 2 leads to an increase in the pH value (a shift to the alkaline side). On the contrary, darkness causes an increase in CO 2 (due to the fact that CO 2 is released during respiration and is not used in the process of photosynthesis) and a decrease in pH (shift to the acid side). Changing the pH value leads to a change in the activity of enzyme systems. In particular, a shift in the pH value to the alkaline side increases the activity of enzymes involved in the breakdown of starch, while a shift to the acid side increases the activity of enzymes involved in the synthesis of starch. The breakdown of starch into sugars causes an increase in the concentration of dissolved substances, in connection with this, the osmotic potential and, as a result, the water potential become more negative. In the guard cells, water begins to flow intensively from the surrounding parenchymal cells. The stomata open. The opposite changes occur when processes shift towards starch synthesis. However, this is not the only explanation. It was shown that the guard cells of the stomata contain significantly more potassium in the light compared to the dark. It has been established that the amount of potassium in the guard cells increases by 4-20 times when the stomata open, while this indicator decreases in the accompanying cells. There is a redistribution of potassium. When the stomata open, a significant gradient of the membrane potential arises between guard and accompanying cells (I.I. Gunar, L.A. Panichkin). The addition of ATP to the epidermis floating on the KC1 solution increases the rate of stomata opening in the light. An increase in the ATP content in the guard cells of the stomata during their opening was also shown (S.A. Kubichik). It can be assumed that ATP formed in the process of photosynthetic phosphorylation in the guard cells is used to enhance the intake of potassium. This is due to the activity of H + -ATPase. Activation of the H + -pump promotes the release of H + from guard cells. This leads to transport along the K+ electrical gradient into the cytoplasm and then into the vacuole. Increased intake of K +, in turn, promotes the transport of C1 - along the electrochemical gradient. Osmotic concentration increases. In other cases, the intake of K + is balanced not by C1 -, but by malic acid salts (malates), which are formed in the cell in response to a decrease in pH as a result of the release of H +. The accumulation of osmotically active substances in the vacuole (K + , C1 - , malates) reduces the osmotic, and then the water potential of the guard cells of the stomata. Water enters the vacuole and the stomata open. In the dark, K+ is transported from the guard cells to the surrounding cells, and the stomata close. These processes are presented in the form of a diagram:

Stomatal movements are regulated by plant hormones (phytohormones). The opening of the stomata is prevented, and the closing is stimulated by the phytohormone - abscisic acid (ABA). It is interesting in this regard that ABA inhibits the synthesis of enzymes involved in the breakdown of starch. There is evidence that under the influence of abscisic acid, the ATP content decreases. At the same time, ABA reduces the intake of K +, possibly due to a decrease in the output of H + ions (inhibition of the H + pump). The role of other phytohormones, cytokinins, in the regulation of stomata opening by enhancing K+ transport to stomatal guard cells and activating H+-ATPase is discussed.

The movement of stomatal cells turned out to be temperature dependent. Studies of a number of plants have shown that stomata do not open at temperatures below 0°C. An increase in temperature above 30°C causes the stomata to close. Perhaps this is due to an increase in the concentration of CO 2 as a result of an increase in the intensity of respiration. However, there are observations that different varieties In wheat, the reaction of stomata to elevated temperatures is different. Prolonged exposure to high temperatures damages the stomata, in some cases so severely that they lose their ability to open and close.

Observations of the degree of openness of the stomata have great importance in physiological and agronomic practice. They help to establish the need to supply the plant with water. Closing of the stomata already speaks of unfavorable shifts in water metabolism and, as a result, of difficulties in feeding plants with carbon dioxide.

Question 1. What body will be discussed? Let's talk about leaves.

Suggest the main question of the lesson. Compare your version with the author's (p. 141). Which plant organ can evaporate water and absorb light?

Question 2. How do algae absorb oxygen, water and minerals? (5th grade)

Algae absorb oxygen, water and minerals throughout the surface of the thallus.

How do plants use light? (5th grade)

Normally, a plant uses sunlight to process the carbon dioxide it needs to live. Thanks to chlorophyll, the substance that colors leaves in green color They are capable of converting light energy into chemical energy. Chemical energy makes it possible to obtain carbon dioxide and water from the air, from which carbohydrates are synthesized. This process is called photosynthesis. At the same time, plants release oxygen. Carbohydrates combine with each other, forming another substance that accumulates in the roots, and thus the substances necessary for the life and development of the plant are formed.

What is a stomata? (5th grade)

Stomata are slit-like openings in the skin of a leaf surrounded by two guard cells. Serve for gas exchange and transpiration.

Leaves of which plants do people harvest for future use and why?

Leaves are harvested medicinal plants(for example, plantain, fireweed, coltsfoot, etc.) for the subsequent preparation of tea, decoctions. Currant leaves are also harvested for tea, mint for tea and cooking. Many dried spices are also made from the leaves.

What gas is released by cells during respiration? (5th grade)

When breathing, oxygen is taken in and carbon dioxide is released.

Question 3. Explain with the help of text and pictures how the structure of a leaf is related to the functions it performs.

Leaf cells rich in chloroplasts are called the main tissue of the leaf, and it performs main function leaves - photosynthesis. Upper layer the main tissue consists of cells tightly pressed to each other in the form of columns - this layer is called columnar parenchyma.

The lower layer consists of loosely arranged cells with extensive gaps between them - it is called spongy parenchyma.

Gases pass freely between the cells of the underlying tissue. The stock of carbon dioxide is replenished by the intake both from the atmosphere and from the cells.

For gas exchange and transpiration, the leaf has stomata.

Question 4. Consider the structure of the sheet in Figure 11.1.

The leaf consists of a leaf blade, petiole (may not be in all leaves, then such a leaf is called sessile), stipules and the base of the leaf blade.

Question 5. There is a contradiction: the photosynthetic cells of the leaf need to be packed more densely, but the movement of gases cannot be prevented. Look at Figure 11.2 and explain how the structure of the leaf resolves this contradiction.

In the leaf parenchyma there are air cavities that solve this problem. These cavities are associated with external environment through stomata and lenticels. The stems and roots of aquatic, marsh and other plants that live in conditions of lack of air and, as a result, difficult gas exchange are rich in air cavities.

Conclusion: leaves carry out photosynthesis, evaporate water, absorb carbon dioxide and release oxygen, protect the kidneys and store nutrients.

Question 6. What are the functions of the sheet?

Leaves evaporate water, absorb carbon dioxide and release oxygen during photosynthesis, protect the kidneys and store nutrients.

Question 7. What happens in the leaf with oxygen and carbon dioxide?

Carbon dioxide absorbed from the atmosphere + water (already in the leaves) in the leaves under the action of sunlight converted into organic matter and oxygen. The latter is released by the plant into the atmosphere.

Question 8. What happens in the leaf with water?

Part of the water entering the leaves evaporates, and part is used in the process of photosynthesis.

Question 9. What fabrics does the sheet consist of?

The leaf is covered with an integumentary tissue - the epidermis. Cells rich in chloroplasts are called the main tissue of the leaf. The upper layer of the main tissue consists of cells tightly pressed against each other in the form of columns - this layer is called the columnar parenchyma. The lower layer consists of loosely arranged cells with extensive gaps between them - it is called spongy parenchyma.

Gases freely pass between the cells of the main tissue due to the air parenchyma. For gas exchange and transpiration, the leaf has stomata.

The thickness of the main tissue of the leaf is penetrated by conductive tissues - bundles of vessels consisting of xylem and phloem. Vessel bundles are reinforced with long and thick-walled cells of the supporting tissue - they give the sheet additional rigidity.

Question 10. What are the functions of leaf veins?

Veins are transport highways of two directions. Together with mechanical fibers, the vein forms a rigid frame of the leaf.

Question 11. What is the danger of overheating and hypothermia of the sheet?

At too high a temperature, as at too low a temperature, photosynthesis stops. Neither organic matter nor oxygen is produced.

Question 12. How is the separation of the leaf from the branch?

Nutrients leave the leaves and are deposited in the roots or shoots in reserve. In the place where the leaf is attached to the stem, the cells die (a scar is formed), and the bridge between the leaf and the stem becomes brittle, and a weak breeze destroys it.

Question 13. What caused the variety of leaf shapes in plants of different species?

Evaporation from it depends on the shape of the leaf. In plants of a hot and dry climate, the leaves are smaller, sometimes in the form of needles and tendrils. This reduces the surface from which water evaporates. A way to reduce evaporation from large leaves is to overgrow or become covered with a thick cuticle or waxy coating.

Question 14. Why can the shape and size of leaves on one plant vary?

Depending on the environment where these leaves are found. For example, in the arrowhead, the leaves that are in the water are different from the leaves that come to the surface of the water. If this is a terrestrial plant, then it depends on the illumination of the plant by the sun, the degree of proximity of the leaf to the root, the time of leaf blooming.

Question 15. My biological research

A verbal portrait of a leaf can replace its image.

Botanists agreed on what words to call the leaves of one form or another. Therefore, they can recognize a leaf from its verbal portrait without looking into a botanical atlas. However, it is useful for beginners to use their images. Us. 56 shows diagrams where different forms leaf blades, tops and bases of leaf blades, compound leaves (Fig. 11.7–11.11). Use these diagrams to create verbal portraits of plant leaves from a herbarium, botanical atlas or textbook.

For example, in zonal geranium, the leaves are long-petiolate, slightly lobed, round-reniform, light green, pubescent. The edge of the leaf blade is entire. The tops of the leaf blade are rounded, the base of the leaf is heart-shaped.

Laurel noble. In the common people, a leaf is called Bay leaf. The leaves are alternate, short-petiolate, entire, glabrous, simple, 6-20 cm long and 2-4 cm wide, with a peculiar spicy smell; leaf blade oblong, lanceolate or elliptical, narrowed towards the base, dark green above, lighter below.

Norway maple. The leaf shape is simple, whole-separated. The leaves have clear, pronounced veins, have 5 lobes, end with pointed lobes, 3 front lobes are the same, 2 lower ones are slightly smaller. Between the blades there are rounded recesses. The apex of the leaf blade is attenuated, the base of the leaf is heart-shaped. The edge of the leaf blade is entire. The leaves are dark green above, light green below, held on long petioles.

Acacia white. The leaf has an unpaired, complex, consisting of whole, oval or ellipse-like leaflets, at the base of each leaf there are stipules modified into spines.

Birch. Birch leaves are alternate, entire, serrated along the edge, ovate-rhombic or triangular-ovate, with a wide wedge-shaped base or almost truncated, smooth. The venation of the leaf blade is perfect pinnate-nervous (pinnate-marginal): the lateral veins end in teeth.

Rose hip. The leaf arrangement is alternate (spiral); venation is pinnate. Its leaves are compound, pinnate (the top of the leaf ends with one leaflet), with a pair of stipules. Leaflets five to seven, they are elliptical, the edges are serrated, the apex is wedge-shaped, grayish below.

Lesson "Cellular structure of a leaf"

Target: show the relationship between the leaf structure and its functions; develop the concept of the cellular structure of plants; continue building skills independent work with instruments, the ability to observe, compare, contrast, draw their own conclusions; develop love and respect for nature.

Equipment: tables "Variety of leaves", "Cellular structure of the leaf"; herbarium - leaf venation, leaves are simple and complex; houseplants; preparations of the peel of tradescantia leaves, geraniums.

DURING THE CLASSES

Every spring, summer on the streets, squares, in the school yard, and at home - all year round elegant green plants surround us on the windowsills. We are used to them. We are so used to it that we often do not notice the difference between them.

Previously, it seemed to many that all leaves are the same, but the last lesson showed the variety of their amazing forms, their beauty. Let's remember what we've learned.

Plants, depending on the number of cotyledons, are divided into two groups. Which? That's right, monocots and dicots! Now look: it turns out that each leaf knows what class its plant belongs to, and the lace of leaf arrangement helps the leaves make better use of light.

So, take the first envelope. Leaves are in it. different plants. Divide them into two groups according to the type of venation. Well done! And now the leaves from the second envelope are also divided into two groups, but at your discretion. Who can say what principle you were guided by when putting things in order? That's right, you divided the leaves complex and simple.

And now look - on the tables of the task. Please complete them.

1. A sheet is a part .... Leaves are made up of... and... .

2. The figure shows leaves with different types venation. Sign which leaf has which venation.

From external description let's move on to study internal structure sheet. In one of the lessons, we learned that a plant needs a leaf for air nutrition, but how does it work? The leaf consists of cells, while the cells are not the same and perform different functions. What fabric covers the sheet? Integumentary or protective!

In the green chamber
Areas are not measured
Rooms not counted
Walls are like glass
You can see right through everything!
And in the walls - windows,
open themselves
They close themselves!

Let's solve this riddle. The green tower is a leaf, the rooms are cells. Transparent, like glass, the walls are an integumentary fabric. That's what we're going to look at today. To do this, you need to prepare the drug. We learned how to do this correctly when we studied the skin of a leaf.

One student makes a preparation of the skin of the upper side of the leaf, the second - the bottom. Ready and set up the microscope. Let's take a look at the top skin first. Why is she like glass? Because it is transparent and therefore transmits light rays.

And what does "windows in the walls" mean? Try to find them! To do this, it is better to consider the skin of the underside of the leaf. How are some cells different from others?

Stomatal cells form a “window”: they are trailing and, unlike other cells of the integumentary tissue, have a green color, because contain chloroplasts. The gap between them is called stomatal.

Why do you think stomata are needed? To ensure evaporation, penetration of air into the sheet. And they open and close to regulate the penetration of air and water. Consider the differences in the structure of the upper and lower skins. There are more stomata on the underside. Different plants have leaves with different numbers of stomata.

Now we need to document our observations as a lab report. To do this, complete the following tasks.

Laboratory work "Structure of the skin of a leaf"

1. Find colorless cells of the integumentary tissue on the micropreparation, examine them. Describe what shape they have? What is their structure? What role do they play in the life of the leaf?

2. Find the stomata. Draw the shape of the guard cells. Note how the guard cells differ from the cells of the integumentary tissue. Locate the stomatal gap between the guard cells.

3. Sketch the skin in a notebook, in the figure sign: the main cells of the skin, guard cells, stomata, stomatal fissure.