Of particular importance in the life of a plant are stomata related to the epidermal tissue system. The structure of the stomata is so peculiar and their significance is so great that they should be considered separately.

The physiological significance of the epidermal tissue has a dual, largely contradictory character. On the one hand, the epidermis is structurally adapted to protect the plant from drying out, which is facilitated by the tight closure of epidermal cells, the formation of a cuticle and relatively long covering hairs. But on the other hand, the epidermis must pass through itself the masses of water vapor and various gases rushing in mutually opposite directions. Gas and vapor exchange under some circumstances can be very intense. In the plant organism, this contradiction is successfully resolved with the help of stomata. The stoma consists of two peculiarly altered epidermal cells, interconnected by opposite (along their length) ends and called guard cells. The intercellular space between them is called stomatal gap.

Guard cells are so called because they change their shape by active periodic changes in turgor in such a way that the stomatal opening alternately opens and closes. The following two features are of great importance for these stomatal movements. First, the guard cells, unlike the rest of the cells of the epidermis, contain chloroplasts, in which photosynthesis occurs in the light and sugar is formed. The accumulation of sugar as an osmotically active substance causes a change in the turgor pressure of the guard cells in comparison with other cells of the epidermis. Secondly, the shells of guard cells thicken unevenly, therefore, a change in turgor pressure causes an uneven change in the volume of these cells, and, consequently, a change in their shape. A change in the shape of the guard cells causes a change in the width of the stomatal opening. Let's explain this with the following example. The figure shows one of the types of stomata of dicotyledonous plants. The outermost part of the stomata is made up of membranous protrusions formed by the cuticle, sometimes insignificant, and sometimes quite significant. They limit a small space from the outer surface, the lower boundary of which is the stomata gap itself, which is called front patio stomata. Behind the stomata gap, inside, there is another small space, delimited by small internal protrusions of the side walls of the guard cells, called patio stomata. The patio directly opens into a large intercellular space called air cavity.

In the light, sugar is formed in the guard cells, it draws water from neighboring cells, the turgor of the guard cells increases, the thin places of their membrane stretch more than the thick ones. Therefore, the convex protrusions protruding into the stomata gap become flat and the stoma opens. White sugar, for example, turns into starch at night, then the turgor in the guard cells falls, this causes a weakening of the stretching of the thin sections of the membrane, they protrude towards each other and the stoma closes. In different plants, the mechanism of closing and opening of the stomata gap can be different. For example, in grasses and sedges, guard cells have widened ends and narrowed in the middle. The membranes in the middle parts of the cells are thickened, while their expanded ends retain thin cellulose membranes. An increase in turgor causes swelling of the ends of the cells and, as a result, the separation of the direct median parts from each other. This leads to the opening of the stomata.

Features in the mechanism of operation of the stomatal apparatus are created both by the shape and structure of the guard cells, and by the participation in it of the epidermal cells adjacent to the stomata. If the cells directly adjacent to the stomata differ in their appearance from other cells of the epidermis, they are called accompanying cells of the stomata.

Most often, accompanying and trailing cells have a common origin.

The guard cells of the stomata are either somewhat elevated above the surface of the epidermis, or, conversely, lowered into more or less deep pits. Depending on the position of the guard cells in relation to the general level of the epidermal surface, the very mechanism for adjusting the width of the stomatal fissure somewhat changes. Sometimes the guard cells of the stomata become lignified, and then the regulation of the opening of the stomatal fissure is determined by the activity of neighboring epidermal cells. Expanding and shrinking, i.e., changing their volume, they entrain the guard cells adjacent to them. However, often stomata with lignified guard cells do not close at all. In such cases, the regulation of the intensity of gas and vapor exchange is carried out differently (by the so-called incipient drying). In stomata with lignified guard cells, the cuticle often covers with a fairly thick layer not only the entire stomatal opening, but even extends to the air cavity, lining its bottom.

Most plants have stomata on both sides of the leaf or only on the underside. But there are also plants in which stomata are formed only on the upper side of the leaf (on leaves floating on the surface of the water). As a rule, there are more stomata on leaves than on green stems.

The number of stomata on the leaves of different plants is very different. For example, the number of stomata on the underside of a awnless bonfire leaf is on average 30 per 1 mm 2, in a sunflower growing under the same conditions - about 250. Some plants have up to 1300 stomata per 1 mm 2.

In specimens of the same plant species, the density and size of stomata are highly dependent on environmental conditions. For example, on the leaves of a sunflower grown in full light, there were an average of 220 stomata per 1 mm 2 of the leaf surface, and in a specimen grown next to the first, but with slight shading, about 140. On one plant grown in full light, the density stomata increases from the lower leaves to the upper ones.

The number and size of stomata strongly depend not only on the growing conditions of the plant, but also on the internal relationships of life processes in the plant itself. These values ​​(coefficients) are the most sensitive reagents for each combination of factors that determine the growth of a plant. Therefore, the determination of the density and size of the stomata of the leaves of plants grown under various conditions gives some idea of ​​the nature of the relationship of each plant with its environment. All methods for determining the size and number of anatomical elements in one or another organ belong to the category of quantitative-anatomical methods, which are sometimes used in environmental studies, as well as for characterizing varieties of cultivated plants, since each variety of a cultivated plant has certain limits of size and the number of anatomical elements per unit area. The methods of quantitative anatomy can be applied with great benefit both in crop production and in ecology.

Along with stomata intended for gas and vapor exchange, there are also stomata through which water is released not in the form of vapor, but in a drop-liquid state. Sometimes such stomata are quite similar to ordinary ones, only somewhat larger than them, and their guard cells are devoid of mobility. Quite often, in a fully mature state, such a stomata lacks guard cells and only a hole remains, bringing water out. Stomata that secrete liquid water are called water, and all formations involved in the release of drop-liquid water - hydathodes.

The structure of hydathodes is varied. Some hydathodes have a parenchyma under the opening that removes water, which is involved in the transfer of water from the water supply system and in its release from the organ; in other hydathodes, the plumbing system goes directly to the outlet. Hydathodes are especially often formed on the first leaves of seedlings of various plants. So, in humid and warm weather, young leaves of cereals, peas and many meadow grasses release water drop by drop. This phenomenon can be observed in the first half of summer in the early morning of every fine day.

The most well-defined hydathodes are located along the edges of the leaves. Often, one or more hydathodes are borne by each of the teeth that turn off the edges of the leaves.

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Who published this discovery in 1675 in his work Anatome plantarum. However, he did not understand their true function. At the same time, his contemporary Nehemiah Grew developed the hypothesis of the participation of stomata in the ventilation of the internal environment of the plant and compared them with the tracheae of insects. Progress in the study came in the 19th century, and at the same time, in 1827, the word "stoma" was first used by the Swiss botanist Decandole. The study of stomata at that time was carried out by Hugo von Mol, who discovered the basic principle of opening stomata, and Simon Schwendener, who classified stomata by the type of their construction.

Some aspects of the functioning of stomata continue to be intensively studied at the present time; The material is mainly Commelina vulgaris ( Commelina communis), garden bob ( Vicia faba), Sweet corn ( Zea mays).

Structure

The size of the stomata (length) ranges from 0.01-0.06 mm (the stomata of polyploid plants are also larger in leaves growing in the shade. The largest stomata were found in an extinct plant Zosterophyllum, 0.12 mm (120 µm) Pore consists of a pair of specialized cells called guard cells (cellulae claudentes), which regulate the degree of openness of the pore, between them is the stomatal gap (porus stomatalis). The walls of the guard cells are thickened unevenly: those directed towards the gap (abdominal) are thicker than the walls directed away from the gap (dorsal). The gap can expand and narrow, regulating transpiration and gas exchange. When there is little water, the guard cells are tightly adjacent to each other and the stomatal opening is closed. When there is a lot of water in the guard cells, it presses on the walls and the thinner walls stretch more, and the thicker ones are drawn inward, a gap appears between the guard cells. Under the gap there is a substomatal (air) cavity, surrounded by cells of the pulp of the leaf, through which gas exchange takes place directly. Air containing carbon dioxide (carbon dioxide) and oxygen penetrates into the leaf tissue through these pores, and is further used in the process of photosynthesis and respiration. Excess oxygen produced during photosynthesis by the inner cells of the leaf is released back into the environment through the same pores. Also, in the process of evaporation, water vapor is released through the pores. Epidermal cells adjacent to the trailing cells are called accompanying (side, neighboring, parotid). They are involved in the movement of guard cells. Trailing and accompanying cells form a stomatal complex (stomatal apparatus). The presence or absence of stomata (the visible parts of the stomata are called stomatal lines) is often used in the classification of plants.

Stomata types

The number of accompanying cells and their location relative to the stomatal opening make it possible to distinguish a number of types of stomata:

• anomocytic - accompanying cells do not differ from the rest of the cells of the epidermis, the type is very common for all groups of higher plants, with the exception of conifers;
• diacytic - characterized by only two accompanying cells, the common wall of which is at right angles to the trailing cells;
• paracytic - accompanying cells are located parallel to the closing and stomatal gaps;
• anisocytic - guard cells are surrounded by three accompanying cells, one of which is noticeably larger or smaller than the others, this type is found only in flowering plants;
• tetracytic - four accompanying cells, characteristic of monocots;
• encyclocytic - accompanying cells form a narrow wheel around guard cells;
• actinocytic - several accompanying cells, radially diverging from the trailing cells;
• pericytic - the guard cells are surrounded by one secondary accompanying cell, the stomata is not connected to the accompanying cell by an anticlinal cell wall;
• desmocytic - guard cells are surrounded by one accompanying cell, the stoma is connected to it by an anticlinal cell wall;
• polocytic - guard cells are not completely surrounded by one accompanying one: one or two epidermal cells adjoin one of the stomatal poles; the stoma is attached to the distal side of a single accompanying cell, which is U-shaped or horseshoe-shaped;
• stephanocyte - a stomata surrounded by four or more (usually five to seven) poorly differentiated accompanying cells, forming a more or less distinct rosette;
• laterocyte - this type of stomatal apparatus is considered by most botanists as a simple modification of the anomocytic type.

In dicots, the paracytic type of stomata is common. The trailing cells of a kidney-shaped (bean-shaped) shape - as they are visible from the surface of the leaf - carry chloroplasts, thin, unthickened sections of the membrane form protrusions (spouts) covering the stomatal gap.

The outer walls of the guard cells usually have outgrowths, which is clearly seen in the transverse section of the stomata. The space bounded by these outgrowths is called the front yard. Quite often, similar outgrowths are observed in the inner membranes of guard cells. They form a backyard, or inner courtyard, connected to a large intercellular space - the substomatal cavity.

In monocots, the paracytic structure of stomata was noted in cereals. The guard cells are dumbbell-shaped - narrowed in the middle part and expanded at both ends, while the walls of the expanded areas are very thin, and in the middle part of the guard cells they are very thickened. Chloroplasts are located in the vesicular endings of cells.

Guard cell movement

The mechanism of movement of guard cells is very complex and varies in different species. In most plants, with unequal water supply at night, and sometimes during the day, the turgor in the guard cells decreases, and the stomatal gap closes, thereby reducing the level of transpiration. With an increase in turgor, the stomata open. It is believed that the main role in the change in turgor belongs to potassium ions. The presence of chloroplasts in the guard cells is essential in the regulation of turgor. The primary starch of chloroplasts, turning into sugar, increases the concentration of cell sap. This contributes to the influx of water from neighboring cells and an increase in turgor pressure in guard cells.

Location of stomata

Dicotyledonous plants tend to have more stomata at the bottom of the leaf than at the top. This is due to the fact that the upper part of a horizontally arranged leaf, as a rule, is better lit, and a smaller number of stomata in it prevents excessive evaporation of water. Leaves with stomata located on the underside are called hypostomatic.

In monocot plants, the presence of stomata in the upper and lower parts of the leaf is different. Very often the leaves of monocotyledonous plants are arranged vertically, in which case the number of stomata on both parts of the leaf may be the same. Such leaves are called amphistomatic.

Floating leaves on the underside of the leaf lack stomata, as they can absorb water through the cuticle. Leaves with stomata located on the upper side are called epistomatic. Underwater leaves have no stomata at all.

The stomata of coniferous plants are usually hidden deep under the endodermis, which makes it possible to greatly reduce water consumption in winter for evaporation, and in summer during drought.

Mosses (with the exception of anthocerotes) have no true stomata.

Stomata also differ in their level of location relative to the surface of the epidermis. Some of them are located flush with other epidermal cells, others are raised above or immersed below the surface. In monocots, whose leaves grow predominantly in length, the stomata form regular parallel rows, while in dicots they are arranged randomly.

Carbon dioxide

Since carbon dioxide is one of the key reactants in the process of photosynthesis, most plants have stomata open during the daytime. The problem is that when the air enters, it mixes with the water vapor evaporating from the leaf, and so the plant cannot get carbon dioxide without losing some water at the same time. Many plants have protection against water evaporation in the form of wax deposits that clog their stomata.

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Notes

Literature

• // Encyclopedic Dictionary of Brockhaus and Efron: in 86 volumes (82 volumes and 4 additional). - St. Petersburg. , 1890-1907.
• Atlas of plant anatomy: textbook. manual for universities / Bavtuto G. A., Eremin V. M., Zhigar M. P. - Mn. : Urajay, 2001. - 146 p. - (Study and textbooks for universities). - ISBN 985-04-0317-9.
• Colin Michael Willmer, Mark Fricker. Stomata. - Chapman & Hall, 1995. - ISBN 0412574306.

Footnotes

An excerpt characterizing the Stoma

Suddenly everything stirred, the crowd began to talk, moved, parted again, and between the two parted rows, at the sound of music playing, the sovereign entered. Behind him were the owner and mistress. The emperor walked quickly, bowing to the right and left, as if trying to get rid of this first minute of the meeting as soon as possible. The musicians played Polish, known then for the words composed on it. These words began: “Alexander, Elizabeth, you delight us ...” The sovereign went into the living room, the crowd rushed to the doors; several faces with changed expressions hurried back and forth. The crowd again retreated from the doors of the drawing room, in which the sovereign appeared, talking with the hostess. Some young man with a confused look was advancing on the ladies, asking them to step aside. Some ladies with faces expressing complete forgetfulness of all the conditions of the world, spoiling their toilets, crowded forward. Men began to approach the ladies and line up in Polish pairs.
Everything parted, and the emperor, smiling and out of time leading the mistress of the house by the hand, went out of the doors of the drawing room. He was followed by the owner with M.A. Naryshkina, then envoys, ministers, various generals, whom Peronskaya called incessantly. More than half of the ladies had cavaliers and were walking or preparing to go to Polskaya. Natasha felt that she remained with her mother and Sonya among the smaller part of the ladies pushed back to the wall and not taken in Polskaya. She stood with her slender arms lowered, and with a measuredly rising, slightly defined chest, holding her breath, with shining, frightened eyes, she looked ahead of her, with an expression of readiness for the greatest joy and the greatest grief. She was not interested in either the sovereign or all the important persons that Peronskaya pointed out - she had one thought: “is it really that no one will come up to me, is it really that I will not dance between the first, is it possible that all these men who now, it seems that they don’t see me, but if they look at me, they look with such an expression, as if they say: Ah! it's not her, so there's nothing to see. No, it can't be!" she thought. “They must know how I want to dance, how well I dance, and how fun it will be for them to dance with me.”
The sounds of Polish, which had gone on for quite some time, were already beginning to sound sad, a memory in Natasha's ears. She wanted to cry. Peronskaya moved away from them. The count was at the other end of the hall, the countess, Sonya and she stood alone as if in a forest in this alien crowd, uninteresting and unnecessary to anyone. Prince Andrei walked past them with some lady, apparently not recognizing them. The handsome Anatole, smiling, said something to the lady he was leading, and looked at Natasha's face with the look with which they look at the walls. Boris walked past them twice and each time turned away. Berg and his wife, who were not dancing, approached them.
This family rapprochement here, at the ball, seemed insulting to Natasha, as if there was no other place for family conversations except at the ball. She did not listen and did not look at Vera, who was saying something to her about her green dress.
Finally, the sovereign stopped beside his last lady (he was dancing with three), the music stopped; the preoccupied adjutant ran up to the Rostovs, asking them to move somewhere else, although they were standing against the wall, and the distinct, cautious and fascinatingly measured sounds of a waltz rang out from the choir. The emperor looked at the hall with a smile. A minute passed and no one started yet. The adjutant manager approached Countess Bezukhova and invited her. She raised her hand, smiling, and laid it, without looking at him, on the adjutant's shoulder. The adjutant manager, a master of his craft, confidently, leisurely and measuredly, tightly hugging his lady, set off with her first on a glide path, along the edge of the circle, at the corner of the hall, grabbed her left hand, turned her, and because of the ever faster sounds of music, only measured the clicks of the spurs of the aide-de-camp's quick and agile feet, and every three beats at the turn, the fluttering velvet dress of his lady seemed to flare up. Natasha looked at them and was ready to cry that it was not she who was dancing this first round of the waltz.
Prince Andrei, in his colonel's white (for cavalry) uniform, in stockings and boots, lively and cheerful, stood in the forefront of the circle, not far from the Rostovs. Baron Firgof spoke to him about tomorrow, the proposed first meeting of the State Council. Prince Andrei, as a person close to Speransky and participating in the work of the legislative commission, could give correct information about the meeting of tomorrow, about which there were various rumors. But he did not listen to what Firgof told him, and looked first at the sovereign, then at the gentlemen who were about to dance, who did not dare to enter the circle.
Prince Andrei watched these cavaliers and ladies, timid in the presence of the sovereign, dying from the desire to be invited.
Pierre went up to Prince Andrei and grabbed his hand.
- You always dance. Here is my protegee [favorite], young Rostova, invite her, - he said.
- Where? Bolkonsky asked. “I’m sorry,” he said, turning to the baron, “we will finish this conversation in another place, but at the ball we have to dance.” - He stepped forward, in the direction that Pierre indicated to him. Natasha's desperate, fading face caught Prince Andrei's eyes. He recognized her, guessed her feelings, realized that she was a beginner, remembered her conversation at the window, and with a cheerful expression approached Countess Rostova.
“Let me introduce you to my daughter,” said the countess, blushing.
“I have the pleasure of being acquainted, if the countess remembers me,” said Prince Andrei with a courteous and low bow, completely contradicting Peronskaya’s remarks about his rudeness, going up to Natasha, and raising his hand to hug her waist even before he finished the invitation to dance. He suggested a waltz tour. That fading expression on Natasha's face, ready for despair and delight, suddenly lit up with a happy, grateful, childish smile.
“I have been waiting for you for a long time,” as if this frightened and happy girl said, with her smile that appeared from ready tears, raising her hand on Prince Andrei’s shoulder. They were the second couple to enter the circle. Prince Andrei was one of the best dancers of his time. Natasha danced superbly. Her feet in ballroom satin shoes quickly, easily and independently of her did their job, and her face shone with the delight of happiness. Her bare neck and arms were thin and ugly. Compared to Helen's shoulders, her shoulders were thin, her chest indefinite, her arms thin; but Helen already seemed to have varnish from all the thousands of glances that glided over her body, and Natasha seemed like a girl who was naked for the first time, and who would be very ashamed of it if she had not been assured that it was so necessary.
Prince Andrei loved to dance, and wanting to quickly get rid of the political and intelligent conversations with which everyone turned to him, and wanting to quickly break this annoying circle of embarrassment formed by the presence of the sovereign, he went to dance and chose Natasha, because Pierre pointed her out to him. and because she was the first of the pretty women that caught his eye; but as soon as he embraced this thin, mobile body, and she moved so close to him and smiled so close to him, the wine of her charms hit him in the head: he felt revived and rejuvenated when, catching his breath and leaving her, he stopped and began to look on the dancers.

It is known that environmental pollution primarily affects the stomatal apparatus of plants. The main functions of stomata are gas exchange and transpiration. Violation of the functions of these stomata can lead to the death of leaves, and, in general, to the death of the entire plant (Lykshitova, 2013). We counted the number of stomata on the leaf blades of the studied plant species in key areas in comparison with the control. Research data are shown in Fig.16.

Rice. 16 Number of stomata on leaf blades Ulmus pumila, Malus baccata, Syringa vulgaris per 1 mm І sheet area

The calculation of the number of stomata per unit area of ​​the leaf blade in woody plants growing in urban conditions showed that, indeed, when approaching the highway, the number of stomata increases. The influence of atmospheric pollution disrupts the integrity of the stomatal cells, and the guard cells of the stomata lose their ability to regulate the width of the stomatal gap.

With constantly open stomatal slits, the consumption of moisture by the plant organism on physiological processes especially affects the intensity of transpiration.

A decrease in the total water content of tissues and an increase in the amount of bound water over the amount of free water may indicate the adaptation of plants to the conditions of the urban environment. As bioindicative indicators of the urban environment, one can use the morphobiological indicators of woody plants, the percentage of dust pollution, and the features of the fractional composition of water.

From the presented figure, it can be seen that in the control plot, the largest number of stomata is observed in the squat elm and is 138, in the apple tree -127, in the lilac -100. Under conditions of environmental pollution, the number of stomata on the leaf blades of all studied species increases sharply. This is a morphological adaptive adaptation to the survival of plants in conditions of atmospheric pollution. An increase in the number of stomata on leaf blades compensates for the decrease in leaf dispersion, as shown earlier. This is due to the fact that a decrease in the area of ​​leaves leads to a reduction in the stomatal apparatus, therefore, an increase in the number of stomata with a decrease in the total area of ​​leaf blades contributes to the preservation of the functions of gas exchange and transpiration of leaves. Data on the number of stomata correlate well with data on leaf dispersion. As mentioned earlier, the greatest decrease in leaf dispersion was observed in elm. Data on the number of stomata indicate that the decrease in the number of leaves per square meter in elm was compensated by a sharper increase in the number of stomata. So, on average, in three plots, the number of stomata in the squat elm increased by 321 in comparison with the reference plot, while in apple and lilac 175 and 106, respectively.

This indicates that the elm adapts well to adverse environmental conditions.

Thus, it can be noted that in the conditions of technogenic pollution of the atmosphere of the city of Ulan-Ude, both tree life forms (apple and elm) and shrubs (lilac) adapt quite well to atmospheric pollution. In all species, morphological mechanisms of adaptation are activated. In conditions of more severe dust pollution, tree forms can be recommended - apple and elm.

Determination of the state of stomata in indoor plants

The leaf of a plant performs various functions. This is the main organ in which photosynthesis, gas exchange and transpiration (evaporation of water) take place. For the implementation of gas exchange in the terrestrial organs of the plant, there are special formations - stomata.

Stomata, although they are part of the epidermis (leaf skin), are a special group of cells. The stomatal apparatus consists of two guard cells, between which there is a stomatal gap, 2–4 peristomatal cells, and a gas-air chamber located under the stomatal gap.

The guard cells of the stomata have an elongated-curved, "bean-shaped" shape. Their walls facing the stomatal fissure are thickened. Stomatal cells are able to change their shape - due to this, the opening or closing of the stomatal gap occurs. These cells contain chloroplasts (green plastids). The opening and closing of the stomatal fissure occurs due to changes in turgor (osmotic pressure) in guard cells. The chloroplasts of the guard cells contain starch, which can be converted into sugar. When starch is converted to sugar, the osmotic pressure increases and the stomata open. With a decrease in sugar content, the reverse process occurs, and the stomata close.

Stomatal slits are often wide open early in the morning and closed (or semi-closed) during the daytime. The number of stomata depends on environmental conditions (temperature, light, humidity). The degree of their disclosure at different times of the day varies greatly in different species. In the leaves of plants in humid habitats, the density of stomata is 100–700 per 1 mm2.

Most land plants have stomata only on the underside of the leaf. They can also be found on both sides of the leaf, as, for example, in cabbage or sunflower. At the same time, the density of stomata on the upper and lower sides of the leaf is not the same: cabbage has 140 and 240 per 1 mm 2, and sunflower has 175 and 325 per 1 mm 2, respectively. In aquatic plants, such as water lilies, stomata are located only on the upper side of the leaf with a density of about 500 per 1 mm 2. Underwater plants do not have stomata at all.

Goal of the work:

determination of the state of stomata in various indoor plants.

Tasks

1. To study the question of the structure, location and number of stomata in various plants according to additional literature.

2. Select plants for research.

3. Determine the state of stomata, the degree of their opening in various indoor plants available in the biology room.

Materials and methods

The state of stomata was determined according to the method described in the Guidelines for Plant Physiology (compiled by E.F. Kim and E.N. Grishina). The essence of the technique is that the degree of opening of the stomata is determined by the penetration of certain chemicals into the pulp of the leaf. Various liquids are used for this purpose: ether, alcohol, gasoline, kerosene, benzene, xylene. We used alcohol, benzene and xylene provided to us in the chemistry lab. The penetration of these fluids into the flesh of the leaf depends on the degree of opening of the stomata. If a light spot appears on the leaf 2–3 minutes after applying a drop of liquid to the underside of the leaf blade, this means that the liquid penetrates through the stomata. In this case, alcohol penetrates into the leaf only with wide open stomata, benzene already with an average opening width, and only xylene penetrates through almost closed stomata.

At the first stage of the work, we tried to establish the possibility of determining the state of stomata (degree of opening) in various plants. Agave, cyperus, tradescantia, geranium, oxalis, syngonium, Amazonian lily, begonia, sanchetia, dieffenbachia, clerodendron, passionflower, pumpkin and beans were used in this experiment. Oxalis, geranium, begonia, sanchetia, clerodendron, passionflower, pumpkin and beans were selected for further work. In other cases, the degree of stomata opening could not be determined. This may be due to the fact that agave, cyperus, lily have rather hard leaves covered with a coating that prevents the penetration of substances through the stomatal gap. Another possible reason could be that by the time of the experiment (14.00 h) their stomata were already closed.

The study was carried out during the week. Every day after school, at 14.00, we determined the degree of stomata opening using the above method.

Results and discussion

The data obtained are presented in the table. The given data are averaged, because on different days, the state of the stomata was not the same. So, out of six measurements, a wide opening of stomata was recorded twice in oxalis, once in geranium, and an average degree of opening of stomata was recorded twice in begonia. These differences do not depend on the time of the experiment. Perhaps they are related to climatic conditions, although the temperature regime in the study and the illumination of plants were fairly constant. Thus, the obtained averaged data can be considered a certain norm for these plants.

The conducted research indicates that in different plants at the same time and under the same conditions, the degree of opening of stomata is not the same. There are plants with wide open stomata (begonia, sanchetia, pumpkin), the average size of the stomatal gap (sour, geranium, beans). Narrow stomatal slits are found only in Clerodendron.

We regard these results as preliminary. In the future, we plan to establish whether and how biological rhythms differ in the opening and closing of stomata in different plants. To do this, timing of the state of stomatal fissures during the day will be carried out.