The main forms of manifestation of the irritability of organisms are various types of motor reactions that are carried out by the whole organism or its individual parts. Obviously, it is only with the help of movement that an organism or an organ can reasonably change its position, optimize its position in space, avoiding the impact of adverse factors or, conversely, effectively use their favorable effect.

The most common motor reactions of living organisms to changes in environmental conditions are taxis, muscular movements, and in plants (except taxis) - tropisms, nastia, nutations and autonomous movements.

Taxis are the movements of the whole, existing independently, of a unicellular or multicellular organism, manifested in its spatial movement relative to the stimulus (movements of protozoa, algae). Depending on the nature of the body's response, taxis can be positive when the movement is in the direction of the acting factor, and negative when the movement is in the opposite direction.

Taxis are classified according to the type of stimulus: phototaxis, chemotaxis, thermotaxis. An example of a positive phototaxis there may be an oriented movement of flagellated unicellular algae to the zone of optimal illumination, the orientation of chloroplasts in the cells of the leaf mesophyll, chemotaxis- accumulation of bacterial cells near a lump of food, the movement of leukocytes to bacteria, etc., thermotaxis- accumulations of unicellular organisms in the zone of optimal temperature.

A necessary condition for irritability is the reversibility of partial changes in structural proteins, the restoration of their previous state. In general, representatives of the animal world are specific in terms of irritability, as they lead a mobile lifestyle, have special organs of movement on a muscular basis, a nervous system with analyzers, and have complex forms of irritability - instinct, conditioned and unconditioned reflexes.

A change in the spatial position of the organs of a plant organism can be carried out: 1) due to the uneven growth of individual parts of the organ; 2) due to temporary changes in the permeability of the cytoplasm of cells, which in most cases leads to a decrease in turgor pressure in them and, accordingly, to a change in the position of the organ. The active movements of the plant organism are also based on the phenomena of irritability and contractility of the proteins of the cytoplasm of plant cells, which are combined with growth and other processes.

The directional orientation of organs and parts of plants in space is an important adaptation that allows them to most effectively use sources of nutrition, water, light and at the same time protect themselves from the adverse effects of various factors.

Tropisms are a motor reaction of organs and parts of plants to the unilateral influence of an environmental factor - light, gravity, water, chemicals, etc. Depending on the nature of the response of the plant organism, tropisms can be positive and negative.

Geotropism is the growth response of individual plant organs to the unilateral influence of the earth's gravity. There are three types of geotropism: positive- when the organ grows vertically down, negative- when the direction of movement is opposite, i.e. up and transverse, or diageotropism,- when the body tries to take a horizontal position. The main taproots are characterized, as a rule, by positive geotropism; branches of the first order of woody plants, stems of monocots, as well as petioles of leaves of many plants - negative; many rhizomes, lateral roots, lateral branches of some conifers, root hairs - transverse.

Of particular interest is the study of growth processes and geotropism phenomena under weightless conditions. The absence of gravitational influence on the studied plants during long-term space flights aboard orbital stations usually caused disordered growth of higher plants, as well as its premature termination. If, however, conditions are created that partially compensate for the absence of the gravitational factor (one-sided illumination, electric current, artificial gravity, etc.), the growth and development of plants are normalized, as evidenced by the formation of seeds in experimental Arabidopsis plants during a long flight of cosmonauts V. V Lebedev and A. N. Berezovoy in 1982

Phototropism. A sign of this type of movement is a clearly expressed positive or negative reaction of organs and parts of plants to a unilateral exposure to light.

Under natural conditions in open areas, phototropism, as a rule, does not clearly manifest itself, since, in addition to direct sunlight, the plant is affected by a relatively strong scattered radiant flow of the sky and clouds. With unilateral exposure to light (near buildings, in a room), the phototropism of individual shoots, even of the entire above-ground part, manifests itself especially clearly - the plants seem to reach for the light.

In the long process of evolution, plant organisms are constantly in the field of terrestrial magnetism and, of course, respond to the influence of a magnetic field. This type of movement is called magnetotropism. An example of it is the increased growth of roots oriented towards the south pole of the Earth or an artificial magnet.

Other physical and chemical factors can also have a unilateral effect on growing organs. Accordingly, they distinguish: chemotropisms, hydrotropisms, thermotropisms, traumatotropisms (i.e., the classification of tropisms depends on the natural source of irritation). Root chemotropism is most indicative, as a result of which an effective search and absorption of mineral nutrition elements from the substrate is carried out.

Nastia. To nastic belong movements that are the response of organs or parts of a plant to the action of stimuli that do not have a specific direction, but affect diffusely and evenly from different sides.

Depending on the direction of movement and the nature of the influencing factor, nastic movements are classified as epinasty - bending an organ (usually a leaf) down due to accelerated growth or turgor stretching of the upper side of the petiole base (lowering leaves of mimosa, white acacia).

Hyponastia - bending the organ upward due to the accelerated growth or stretching of the cells of the lower side of the petiole and the central vein, as well as due to the corresponding contractions of the tissues of the upper side (lifting the leaf blades up at night in the quinoa, tobacco).

Niktynastia - motor reactions caused by the onset of darkness, the so-called sleep of plants (closing flowers, lowering carrot inflorescences at night).

Photonasty - opening of flower petals with increased lighting (chicory, dandelion, potato inflorescences).

Thermonastia - opening flowers when the temperature rises (tulip, crocus, coltsfoot, garden poppy).

Seismonasty - movements of plant organs that are a response to a blow or concussion (mimosa, sour, purslane).

Nutations - the ability of plants to circular or pendulum movements due to periodically repeated changes in turgor pressure and growth intensity of opposite sides of a particular organ. Best of all, such movements are expressed at the tops of the stems and tendrils of climbing plants. Such plants are called climbing or creepers. Among them, according to the method of attachment, they distinguish curly, clingy and plants thatintertwined.

At climbing plants the tip during growth makes uniform nutational movements and, upon contact with the support, begins to wrap around it (hops, morning glory, beans). tenacious plants have tendrils of different origin, which, twisting or sticking to a support, form a strong and elastic suspension of plants (grapes, bryonia, pumpkin, vetch, peas). Tenacious climbing plants also include those in which sharp hooks or thorns are formed on the stem, leaf petioles (rose hip, wood pliers, Velcro, blackberry) that hold the stem on a support.

For plants, which intertwined characteristic is the placement of lateral branches perpendicular to the main stem, which support the stem on random supports or other plants (raspberries, veronica, midges).

Also interesting are the movements of organs in insectivorous plants (sundew, bladderwort, venus flytrap, etc.). The sensitive structures of these plants (glandular hairs, etc.) are more sensitive than the organs of touch in humans.

The movements that a plant or its organ performs due to the physico-chemical changes in its dead constituents can be called passive. (hygroscopic), since in the absolute majority these movements are due to a change in the amount of water in the colloids that make up the cell membrane or are the remains of the contents of the cell. Most often they are implemented in throwing and mobile devices for distributing fruits and seeds (scales of pine cones, valves of mature beans of yellow acacia, etc.). Ch. Darwin, J. Sachs, G. Gaberlandt, Jagadis-Chandra Bos, N. G. Kholodny, I. I. Gunar, F. Vent.

Kholodny Nikolai Grigorievich (1882-1953) - Soviet botanist-phytophysiologist and microbiologist, acad. AN Ukrainian SSR. Known for his fundamental works on plant physiology and ecology, microbiology and soil science. One of the founders of the theory of plant hormones, the author of the hormonal theory of tropisms (known in the literature as the Kholodny-Went theory). The Institute of Botany of the Academy of Sciences of the Ukrainian SSR is named after him.

The physiological basis of the transmission of irritation in the animal body is determined by changes in the electrical charge that passes through the cell and releases the hormone, which serves as a connecting bridge between cells, causing changes in the permeability in neighboring cells. It is believed that the carrier of information about irritation is acetylcholine.

In plants, the main irritants are light, chemical compounds, changes in concentration, and the carrier of information, obviously, is phytohormones, phytochrome and biopotentials.

Almost all types of movements represent a certain reaction of organisms to certain changes in the environment, a reaction aimed at maintaining or creating such conditions and conditions under which individual organs and the entire organism could best perform their characteristic functions. It was this purposefulness of motor reactions that was first noticed by Charles Darwin.

- A source-

Bogdanova, T.L. Handbook of biology / T.L. Bogdanova [and d.b.]. - K .: Naukova Dumka, 1985. - 585 p.

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IRRITABILITY OF PLANTS

What is irritability? This is the ability of the body to perceive the effects of the external and internal environment and respond by changing the processes of life.

The range of external influences perceived by the plant is wide - light, temperature, gravity, chemical composition of the environment, the Earth's magnetic field, mechanical and electrical irritations.

In plants, just as in animals, the perception of stimulus and the response, such as a motor response, are spatially separated. The transmission of irritation (conduction of excitation) can be carried out by the appearance and propagation of an electrical potential throughout the plant, the so-called. action potential.

The existence of electricity in plants can be verified by fairly simple experiments.

42. Detection of fault currents in a cut apple

The so-called fault currents were first discovered at the end of the 18th century. Italian scientist Luigi Galvani in animal organisms. If you cut the dissected frog muscle across the fibers and bring the electrodes of the galvanometer to the cut and the longitudinal intact surface, the galvanometer will record a potential difference of about 0.1 V

The first evidence of the existence of similar processes in plants was obtained almost 100 years later, when, by analogy, they began to measure damage currents in different plant tissues. Sections of leaves, stems, reproductive organs, and tubers always turned out to be negatively charged with respect to healthy tissue.

So, go back to 1912 and repeat the experiment with measuring the potentials of a notched apple. For the experiment, in addition to an apple, you need a galvanometer capable of measuring a potential difference of about 0.1 V.

Cut the apple in half, remove the core. If both electrodes assigned to the galvanometer are applied to the outer side of the apple (peel), the galvanometer will not record the potential difference. Transfer one electrode to the inside of the pulp, and the galvanometer will note the occurrence of a fault current.

In addition to the apple, fault currents up to 50-70mV can be measured. , in cut stems, petioles, leaves.

As later studies have shown, the average rate of damage current in the stem and petiole is about 15-18 cm/min.

In intact organs, biocurrents also constantly exist, but highly sensitive equipment is needed to measure them.

It has been established that the leaf tissue is charged electronegatively with respect to the central vein, the shoot apex is positively charged with respect to the base, and the leaf blade is positively charged with respect to the petiole. If the stem is placed horizontally, then under the influence of the force of gravity, the lower part of it becomes more electropositive with respect to the upper one.

The presence of bioelectric potentials is characteristic of any cell. The potential difference between the cell vacuole and the external environment is about 0.15 V. Only 1 cm 2 of a leaf can contain 2-4 million cells, and each is a small power plant.

The decisive role in the emergence of vegetable, as well as animal, electricity is played by

cell membranes. Their permeability for cations and anions in the direction from the cell and into the cell is not the same. It has been established that if the concentration of any electrolyte on one side of the membrane is 10 times higher than on the other, then a potential difference of 0.058 V appears on the membrane.

Under the influence of various stimuli, the permeability of membranes changes. This leads to a change in the value of biopotentials and the emergence of action currents. The excitation caused by the stimulus can be transmitted through the plant from roots to leaves, regulating, for example, the work of stomata, the rate of photosynthesis. When lighting changes, air temperature changes, action currents can also be transmitted in the opposite direction - from leaves to roots, which leads to a change in the activity of the root.

Interestingly, biocurrents propagate up the plant 2.5 times faster than down.

With the greatest speed, excitation in plants goes along the conducting bundles, and in them - along the satellite cells of the sieve tubes. The rate of propagation of the action potential (electrical impulses) throughout the plant varies from species to species. Insectivorous plants and mimosa react fastest of all - 2-12 cm / s. In other plant species, this speed is much lower - about 25 cm/min.

43. Green pea experiment

This experiment was first staged by the largest researcher of the problem of plant irritability

Indian scientist D. C. Bose. He shows that a sharp increase in temperature causes the appearance of currents of action in the seeds. For the experiment, several green (immature) seeds of peas, beans, beans, a galvanometer, a dissecting needle, and a spirit lamp are needed.

Connect the outer and inner parts of the green pea with a galvanometer. Very carefully in a bottle, heat the pea (without damaging it) to approximately 60°C.

When the cell temperature rises, the galvanometer registers a potential difference of up to 0.1-2 V. Here is what D. Ch. Bos himself noted about these results: if you collect 500 pairs of halves of peas in a certain order in a series, then the total electrical voltage will be 500 V, which is quite enough for an execution in the electric chair.

The most sensitive cells in plants are the cells of growth points located at the tops of shoots and roots. Numerous shoots, abundantly branching and rapidly growing in length, the tips of the roots, as it were, feel the space and transmit information about it to the depths of the plant. It has been proven that plants perceive a touch to the leaf, reacting to it by changing biopotentials, moving electrical impulses, changing the speed and direction of movement of hormones. For example, the root tip reacts to more than 50 mechanical, physical, biological factors and each time it chooses the most optimal program for growth.

You can make sure that the plant responds to touch, especially frequent, annoying, in the following experiment.

44. Is it worth touching plants unnecessarily

Get acquainted with thigmonasty - motor reactions of plants caused by touch.

For a 2-pot experiment, plant one plant at a time, preferably without drooping leaves (beans, beans). After the appearance of 1-2 leaves, start exposure: rub the leaves of one plant lightly between thumb and forefinger 30-40 times daily for 2 weeks.

By the end of the second week, the differences will be clearly visible: the plant subjected to mechanical irritation lags behind in growth (Fig. 23).

The results of the experiment indicate that prolonged exposure of cells to weak stimuli can lead to inhibition of the vital processes of plants.

Plants planted along the roads are exposed to constant impacts. Spruces are especially sensitive. Their branches, facing the road, on which people often walk, cars drive, are always shorter than the branches located on the opposite side.

The irritability of plants, i.e., their ability to respond to various influences, underlies active movements in plants, which are no less diverse than in animals.

Before proceeding to the description of experiments that reveal the mechanism of plant movement, it is advisable to become familiar with the classification of these movements. If plants

Rice. 23 Influence of mechanical action on plant growth

breathing energy is expended on the implementation of movements, these are physiologically active movements. According to the mechanism of bending, they are divided into growth and turgor.

Growth movements are due to a change in the direction of growth of the organ. These are relatively slow movements, for example bending stems towards light, roots towards water.

Turgor movements are carried out by reversible absorption of water, compression and stretching of special motor (motor) cells located at the base of the organ. These are the rapid movements of plants. They are characteristic, for example, of insectivorous plants, mimosa leaves.

The types of growth and turgor movements will be considered in more detail below as the experiments are carried out.

For the implementation of passive (mechanical) movements, no direct expenditure of cell energy is required. In most cases, the cytoplasm does not participate in mechanical movements. The most common are hygroscopic movements, which are caused by dehydration and depend on the humidity of the air.

HYGROSCOPIC MOVEMENTS

Hygroscopic movements are based on the ability of plant cell membranes to absorb water and swell. When swelling, water enters the space between the molecules of cellulose (cellulose) in the membrane and protein in the cytoplasm of the cell, which leads to a significant increase in the volume of the cell.

45. Movement of the scales of cones of conifers, dry moss, dried flowers

Study the effect of water temperature on the speed of movement of the seed scales of the cones.

For the experiment, you need 2-4 dry cones of pine and spruce, dried inflorescences of pink acroclinium or large helichrysum (immortelle), dry moss of cuckoo flax, a clock.

R
look at a dry pine cone. The seed scales are raised, the places to which the seeds were attached are clearly visible (Fig. 24).

Dip half of the pine cones in cold water, and the second in warm (40-50 ° C). Watch the scales move. Check

Rice. 24. Pine cones.

the time it took for them to close completely.

Take the buds out of the water, shake them off and watch the scales move as they dry.

Mark the time for which the scales will return to their original state, enter the data in the table:

Object of observation	Water temperature		Duration
			closures	opening
pine cones
pine cones
spruce cones
spruce cones
immortelle inflorescence
immortelle inflorescence

Repeat the experiment with the same cones several times. This will allow not only to obtain more accurate data, but also to verify the reversibility of the studied type of movement.

The results of the experiment will allow us to draw important conclusions:

1) The movement of the seed scales of the cones is due to the loss and absorption of water by them. This is also evidenced by the direct dependence of the movement of the scales on the temperature of the water: with its increase, the speed of movement of water molecules increases, the swelling of the scales occurs faster.

2) In order for the swelling of the scales to change their position in space, the structure and chemical composition of the cells on the outer and inner sides of the scale must be different. It really is. The cell membranes of the upper side of the scales of coniferous cones are more elastic, extensible compared to the cells of the lower side. Therefore, when immersed in water, they absorb it more, increase their volume faster, which leads to an elongation of the upper side and downward movement of the scales. In the process of dehydration, the cells of the upper side also lose water faster than the cells of the lower side, which leads to the upward folding of the scales.

It is interesting to observe the swelling-induced movements of the leaves of cuckoo flax or other leafy mosses. In living plants, the leaves are directed away from the stem, while in dry plants, they are pressed against it. If you lower the dry stalk into water, after 1-2 minutes the leaves move from a vertical position to a horizontal one.

The movements of the dried immortelle inflorescence are very beautiful. If the dry inflorescence is lowered into water, after 1-2 minutes the leaves of the wrapper begin to move and the inflorescence closes.

Exercise. Compare the speed of movement of the scales of cones of various types of conifers. Does it depend on the size of the cones? Compare the speed of movement of the scales of pine and spruce cones, moss leaves and leaflets of the immortelle inflorescence involucre, identify similarities and differences.

46. ​​Hygroscopic movements of seeds. Hygrometer from stork seeds

Hygroscopic movements play an important role in seed dispersal of various plants.

Study the mechanism of self-burrowing of stork seeds, movement of field cornflower seeds on the soil.

For the experiment, you need the seeds of a stork (robber), blue cornflower, a sheet of thick paper, a watch, a glass slide.

Stork is a common plant in Belarus. It got its name due to the similarity of the fetus with the head of a stork (Fig. 25).

Consider carefully the structure of the dry fruit of the stork. The lobes of a mature box-shaped fruit are equipped with a long awn, spirally twisted in the lower part. The fruit is covered with hard hairs.

Place a drop of water on a glass slide and drop the dry fruit into it. The spirally twisted lower part begins to unwind

and the fetus, which does not have support on the glass, makes rotational movements.

After complete straightening of the spine, transfer the fruit to the dry part of the glass. As it dries, the lower part spirals again and causes the fruit to rotate.

Spend the timing of the experiment, comparing the speed of the processes of unwinding and twisting of the spiral.

The mechanism of movement of the fruit of the stork is the same as the scales of coniferous cones - the difference in the hygroscopicity of the awn cells.

Observing the movement of a fruit in a drop of water makes it possible to understand its behavior in the soil. When the fruit falls to the ground, the upper end of the awn, bent at a right angle, clings to the surrounding stalks and remains motionless. When twisting and

Rice. 25. Stork.

untwisting the spiral section, the lower part of the fruit with the seed is screwed into the ground. The way back is blocked by hard, bent down hairs covering the fetus.

To make a primitive hygrometer, make a hole in a piece of cardboard or a board covered with white paper and fix the lower end of the fruit in it. To calibrate the device, first dry, then moisten the awn with water and mark the extreme position (Fig. 26). It is better to place the device on the street, where fluctuations in humidity are more pronounced than indoors.

The stork is not the only plant capable of self-burying seeds. Feather grass, wild oat, and foxtail have a similar structure and distribution mechanism.

P cornflower lods (achene with a tuft of hard bristles) are not capable of self-burrowing. With fluctuations in soil moisture, the bristles alternately lower and rise, pushing the fruit forward.

Exercise. Collect seeds of cornflower, foxtail, wild oats. Study their behavior in a wet and dry environment, compare with a stork.

Figure 26. Stork hygrometer.

TROPISM

Depending on the structure of the organ and the action of environmental factors, two types of growth movements are distinguished: tropisms and nastia.

Tropisms (from the Greek "tropos" - turn), tropical movements are movements of organs with radial symmetry (root, stem) under the influence of environmental factors that act on the plant one-sidedly. Such factors can be light (phototropism), chemical factors (chemotropism), the effect of the earth's gravity (geotropism), the Earth's magnetic field (magnetotropism), etc.

These movements allow plants to arrange leaves, roots, flowers in a position that is most favorable for life.

47. Root hydrotropism

One of the most interesting types of movement is the movement of the root towards the water (hydrotropism). Land plants have a constant need for water, so the root always grows in the direction where the water content is higher. Hydrotropism is inherent primarily in the roots of higher plants. It is also observed in moss rhizoids and fern growths.

For the experiment, you need 10-20 pecked pea seeds (lupine, barley, rye), 2 Petri dishes, a little plasticine.

With a plasticine barrier tightly attached to the bottom, divide the area of ​​\u200b\u200bthe cup into 2 equal parts. Place the seeds that have hatched on the barrier, slightly pressing them into the plasticine so that the seeds do not budge when the root grows. The roots should be directed strictly along the barrier (Fig. 27).

These stages of work in the control and experimental cups are the same. Now we have to create various conditions for moisturizing. In the control cup, the humidity in the left and right sides should be the same. In an experimental cup, water is poured into only one half, and the second remains dry.

Rice. 27. Schematic arrangement of seeds in the study of root hydrotropism.

Cover both cups with lids and place in a warm place. Monitor the position of the roots daily. When their orientation becomes clearly visible, count the number of seeds whose roots showed positive hydrotropism (organ growth towards water).

Observations of the movement of the root towards the water clearly show that tropisms are growth movements. The root grows towards the water, while the root bends, if necessary, by the plant.

121

chemicals, the growth zone of the organ, and the bend is formed at some distance from it, i.e., irritation is transmitted along the root (Fig. 28).

Exercise. According to the experimental scheme described above, check the ability of plants to recognize not only water, but also the solutions of mineral salts that the plant needs, for example, a 0.3% solution of potassium or ammonium nitrate.

Rice. 28 Chemotropic root bending

48. The influence of the force of gravity on the growth of the stem and root

Most plants grow vertically. In this case, the main role is played by the

their position relative to the soil surface, and the direction of the radius of the Earth. That is why on the mountain slopes plants grow at any angle to the soil, but upwards. The main stem has a negative geotropism - it grows in the direction opposite to the action of the earth's gravity. The main root, on the contrary, has positive geotropism.

The behavior of lateral shoots and roots is most interesting: unlike the main root and stem, they are able to grow horizontally, possessing intermediate geotropism. Shoots and roots of the second order do not perceive the action of the force of gravity at all and are able to grow in any direction. The unequal perception by shoots and roots of different orders of action of the earth's gravity allows them to be evenly distributed in space.

To be convinced of the opposite reaction of the main stem and the main root to the same effect of the earth's gravity, we can put the following experiment.

For the experiment, you need sunflower seeds that have been hatched, glass and foam plates 10X10 cm, filter paper, plasticine, a glass.

Lay several layers of dampened filter paper on the foam sheet. Place the seeds that have hatched on it so that their sharp ends are pointing down. Attach pieces of plasticine to the corners of the plate. Put a glass plate on them, pressing lightly, to fix the seeds in the desired position. Wrap several layers of moistened filter paper

paper and in an upright position (the sharp ends of the seeds should be pointing down), place in a warm place.

When the roots reach 1-1.5 cm, turn the plate 90 ° so that the roots are horizontal.

Check your seedlings daily. The filter paper must be damp.

Spend the timing of the experiment and note the time (in days from the beginning of the experiment) of the manifestation of the geotropical bend.

The results of the experiment show that at any position of the seedling in space, the main root always bends down, and the stem - up. Moreover, the response of the axial organs can manifest itself quite quickly (1-2 hours).

The geotropic sensitivity of plants is high, some are able to perceive a deviation from the vertical position of 1°. Its manifestation depends on a combination of external and internal conditions. Under the influence of low air temperature, the negative geotropism of the stems can turn into transverse, which leads to their horizontal growth.

How does a stem or root "feel" its position in space? At the root, the zone that perceives geotropic irritation is located in the root cap. If it is removed, the geotropic reaction dies out. In the stem, the forces of gravity are also perceived by the tip.

Current Healing Poisons of Plants The Tale of Phytoncides

Book

Tokin B.P. Healing poisons of plants. The Tale of Phytoncides. Ed. 3rd, rev. and additional - 5 Publishing house of Leningrad. University, 1980.-280 p. Il.-67, bibliography - 31 titles.

Irritability is a universal property of all living things to respond to environmental influences.

From the textbook

§42.IRRITABILITY OF ANIMALS

Basic concepts: IRRITABILITY OF ANIMALS. SENSORS

Remember! What is irritability?

Think

The presence of irritability in plants is proved by research, which demonstrates the growth movements of the root and shoot in the bean seedling. This is due to the fact that the shoot reacts with growth to light, and the root perceives the force of gravity and grows downward. And how to make sure that there is irritability in animals?

I l. 167. Growth movements of a plant

What are the features of the irritability of animals?

Irritability in animals is manifested in the ability to respond to environmental influences with their vigorous activity. For example, on the morning sunrise, birds wake up and begin to sing, or touching a grape snail makes it hide in the plowing. In these examples, light or touch would be the stimulus, the process of this force would be the stimulus, and the response of the birds or snails to the action of the factors would be the biological response. Animals can be irritated by light, mechanical influences, temperature, salt composition of water, food, humidity, water, sounds, chemicals and many other factors.

I l. 168. Finch - one of the most common songbirds

A sign of irritability at the cell level is a positive electric charge on the cell surface and a negative charge inside the cell. This charge difference can change under the influence of various factors, which is the beginning of intracellular processes. Changes in cellular metabolism determine the response of the cell to the impact of the factor. Irritability is also characteristic of the cytoplasm of cells, which is able to perceive environmental influences and respond to them by the appearance or cessation of movement. In multicellular animals, tissues that are characterized by excitability participate in the implementation of irritability. These are nervous, muscular and certain types of epithelial. Carrying out excitation to ensure movement, secretion is associated with such organs as nerves, spinal cord and brain, muscles, secretion glands. In shaping the response of an animal to environmental influences, the nervous and endocrine systems are of decisive importance.

Consequently, IRRITABILITY OF ANIMALS is the ability to move from a state of rest to an active state in response to the action of environmental factors, which is realized at different levels of their organization.

What are the forms of irritability in animals?

The biological response of animals to environmental influences is manifested in the form of taxis and reflexes. In contrast to the growth or hygroscopic movements of plants and fungi, in animals these reactions are motor.

Taxi - a motor reaction in response to the directed influence of a factor, carried out by cells or organisms. For example, the ejection of a thread from the stinging cell of a hydra when touching a sensitive outgrowth is mechanotaxis, and the movement of amoebocytes towards nutrients or from harmful substances is a positive or negative chemotaxis. Taxis provide spatial orientation of animal movements to the action of favorable or unfavorable stimuli.

Reflexes - a motor reaction of the body to a certain starting stimulus, carried out with the obligatory participation of the nervous system. For the first time, reflexes as forms of irritability appear in coelenterates in connection with the emergence of a diffuse nervous system in them. Reflexes can be congenital unconditioned (compression of the body of the hydra into a ball after mechanical impact) or acquired conditioned (food reflexes of fish that are formed when feeding at the same time).

Il. 169. Taxi amebocytes

I l. 170. Hydra's unconditioned protective reflex

Taxis and reflexes are constant components in the behavior of animals. If reflexes determine the occurrence and course of the biological reaction of the animal, then taxis provide its direction. For example, the appearance of a gull with food triggers the reaction of chicks (unconditioned food reflex), and the red spot on its beak directs the reaction of these chicks to its beak (positive phototaxis).

So, the biological reactions of animals to the influence of factors is the relationship of taxis and reflexes.

Il. 171. Forms of irritability in chicks of terns

What is the sign of the sense organs for the organism of animals?

SENSE ORGANS are anatomical formations of the animal body that perceive information from the external or internal environment. This information comes in the form of exposure to sound, light, chemicals and is important for turning on and off various biological reactions.

The main sense organs in animals are the organs of sight, hearing, smell, taste and touch. For mobile animals, balance organs are of great importance. Individual groups of animals may have specific sense organs associated with their lifestyle. So, fish have a lateral line, in pit-headed snakes - organs for the perception of thermal rays, in dolphins and sperm whales - organs for the perception of reflected sounds.

What is the significance of the sense organs for animals?

The most primitive organs of vision, which are light-sensitive eyes (jellyfish, flat free-living worms), allow to distinguish light from darkness. To distinguish the strength and direction of light, to catch the movements of objects, simple eyes (spiders) allow. Compound eyes of insects, cephalopods and vertebrates. Such eyes already distinguish the shape, volume and color of objects. Thanks to the organs of vision, animals orient themselves in the environment, successfully obtain food in the daytime and defend themselves from enemies.

Sound - vibrations of the air or water environment or a solid substrate - plays a dual role in the life of animals. On the one hand, it is a signal of danger, and on the other hand, it is a way of communication. Sound-receiving organs are already in jellyfish. They perceive low-frequency vibrations and will allow you to "foresee" a storm. The perception and reproduction of sounds are well developed in arthropods, in particular insects. their hearing organs can be placed on the legs, abdomen, antennae. The organ of hearing is of the greatest importance for terrestrial vertebrates, therefore, the auditory system is observed in them: amphibians have a tympanic membrane, reptiles have an external auditory canal, birds and some mammals have an external ear, mammals already have all three auditory ossicles.

Sensitivity to chemical stimuli is one of the oldest types of senses. In animals, it is provided by the organs of smell and taste, which play an important role in finding food, individuals of the opposite sex, recognizing individuals of their own species, avoiding predators and harmful influences. Among terrestrial invertebrates, the organs of chemical sense have reached the greatest development in arthropods, especially in insects, and among vertebrates in mammals.

The mechanical effects of the environment (touch, pressure, vibration) in invertebrates perceive sensitive creations of integument in the form of cilia, hairs, antennae, and in vertebrates - skin receptors.

Consequently, the information of the environment is very diverse, therefore, the sense organs in animals are also diverse.

ACTIVITY

Laboratory research

ANIMAL SENSORS

Purpose: to consolidate knowledge about the sense organs of animals; to form the ability to characterize the sense organs of various groups of animals on the example of specific representatives.

Equipment: drawings, collections of insects, wet preparations of crayfish and fish.

Progress

1. Examine the body of a crayfish and determine the name, features and location of the organs of vision, touch, smell and taste.

2. Consider the body of the May beetle and determine the name, features and location of the organs of vision, touch, smell and taste.

3. Examine the body of a river perch and determine the name, features and location of the organs of vision, smell, taste and lateral line.

4. Fill in the table.

Name of the sense organs	Cancer river	May Khrushch	river perch
organs of vision
Olfactory organs
organs of taste
sense organs

5. Formulate a conclusion.

Learning to know

Mini-project "HOW DO ANIMALS SEE?"

For centuries, people did not even know how animals see the world. But today science gives us the opportunity to look into the wonderful world of the diversity of the organs of vision of animals. Use the guideline (see appendix) to create a mini-project and, using the example of the proposed six animals (cat, horse, dragonfly, dove, monkey, snake) or animals that you choose yourself, describe the capabilities of the animals' organs of vision.

RESULT

	Questions for self-control
	1. What is irritability? 2. What is the meaning of irritability? 3. Name the main forms of irritability in animals. 4. Give an example of taxis and reflexes of animals. 5. What are sense organs? 6. Name the main sense organs of animals.
	7. What are the features of the irritability of animals? 8. What are the forms of irritability in animals? 9. What is the significance of the sense organs for the animal organism?
10-12	10. Give a description of the sense organs of different groups of animals, using specific representatives.

Irritability- this is the property of all living things to respond to external influences by changing the structure and functions. All cells and tissues are irritable.

Irritants- these are environmental factors that can cause a response of a living formation.

Irritation- is the process of exposure of the stimulus to the body. In the process of evolution, tissues have been formed that have a high level of irritability and are actively involved in adaptive reactions. They are called excitable tissues. These include nervous, muscular and glandular tissues.

Excitability- this is the ability of highly organized tissues (nervous, muscular, glandular) to respond to irritation by changing the physiological properties and generating the excitation process. The nervous system has the highest excitability, then muscle tissue, and finally glandular cells.

Irritants are external and internal. External are divided into:

physical (mechanical, thermal, radiation, sound irritations)

chemical (acids, alkalis, poisons, medicinal substances)

biological (viruses, various microorganisms)

Internal stimuli include substances that are formed in the body itself (hormones, biologically active substances).

By biological significance, stimuli are divided into adequate and inadequate. Adequate include stimuli that act in natural conditions on excitable systems, for example: light for the organ of vision; sound for the organ of hearing; scent to smell.

Inappropriate time. In order to cause excitation, an inadequate split must be many times stronger than an adequate one for the perceiving apparatus. Excitation is a set of physical and chemical processes in the tissue.

7. Resting potential action potential. local response.

Resting potential.

When a cell or fiber is at rest, its internal potential (membrane potential) varies from -50 to -90 millivolts and is conventionally taken as zero. The presence of this potential is due to the inequality of the concentrations of Na + , K + , Cl - , Ca 2+ ions inside and outside the cell, as well as different membrane permeability for these ions. There is 30-50 times more potassium inside the cell than outside. At the same time, the permeability of the membrane of an unexcited cell for potassium ions is 25 times higher than for sodium ions. Therefore, potassium leaves the cell to the outside. At the floor, the anions of the cytoplasm of the cell, especially the outer ones, pass through the membrane worse, concentrate at its surface, creating a "-" potential. Potassium ions released from the cell are held at the outer surface of the membrane by an electrostatic opposite charge.

This potential difference is called the membrane potential or the resting potential. Over time, in such a situation, most potassium ions could go outside the cell and the difference in their concentrations outside and inside would even out, but this does not happen, because there is a sodium-potassium pump in the cell. Due to which the reverse flow of potassium from the tissue fluid into the cell is carried out and the release of sodium ions against the concentration gradient (and there is more sodium outside the cell)

action potential

If a nerve or muscle fiber is affected differently, then the permeability of the membrane immediately changes. It increases for sodium ions, since the concentration of sodium in the tissue fluid is higher, then the ions rush into the acid, reducing the membrane potential to zero. For some time there is a potential difference with the opposite sign (membrane potential reversion).

a) depolarization phase

b) repolarization phase

c) phase of trace repolarization (potential)

The change in the membrane permeability for Na+ does not last long. It starts to increase for K+ and decreases for Na+. This corresponds to the phase of repolarization. The descending part of the curve corresponds to the trace potential and reflects the recovery processes that occur after irritation.

The amplitude and nature of temporal changes in the action potential (pd) little depends on the strength of the spread. It is important that this force be of a certain critical value, which is called irritation or rheobase. Having arisen at the site of irritation, the action potential propagates along the nerve or muscle fiber without changing its amplitude. The presence of a threshold of stimulation and the independence of the amplitude of the action potential from the strength of the stimulus is called the law of "all" or "nothing". In addition to the strength of irritation, the duration of its action is also important. Too short action time does not lead to excitation. It is difficult to define it methodically. Therefore, the researcher Lapin introduced the term "chronopsia". This is the minimum time required to cause tissue excitation with a force of raz-la equal to two rheobases.

The emergence of an action potential is preceded at the point of irritation of the muscle or nerve by active under threshold changes in the membrane potential. They appear in the form local(local) response.

Local response is characterized by:

dependence on the strength of stimulation

increase in the magnitude of the response.

non-propagation along the nerve fiber.

The first signs of a local response are detected under the action of stimuli that make up 50-70% of the threshold value. The local response, as well as the action potential, is due to an increase in sodium permeability. However, this increase was not enough to elicit an action potential.

An action potential occurs when membrane depolarization reaches a critical level. But the local response is important. It prepares tissues for subsequent exposures.

Conduction of excitation along nerve and muscle fibers. Phase nature of changes in the excitability of nerve fibers.

Carrying out excitation

Excitation spreads through the nerve and muscle fibers due to the formation of an action potential and local electric currents in them. If an action potential is generated in any part of the nerve fiber due to the action of a la, then the membrane in this area will be charged "+". Neighboring unexcited area "-".

A local current occurs, which depolarizes the membrane and contributes to the emergence of an action potential in this area. That. the excitation propagates along the fiber.

Under natural conditions, excitation propagates along the fiber in the form of intermittent pulses of a certain frequency. This is due to the fact that after each impulse, the nerve fiber becomes non-excitable for a short period of time. The change in excitability is examined with the help of 2 stimuli acting at a certain interval.

The following changes in excitability have been established.

Drawing During a local response, excitability is increased. In the phase of depolarization, complete non-excitability of the nerve is noted. This is the so-called absolute refractory phase. The duration of this phase for nerve fibers is 0.2-0.4 mls, for muscles 2.5-4 mls. This is followed by a phase of relative refractoriness. It corresponds to the phase of repolarization.

Nerve and muscle fibers respond with excitation to strong stimuli. The phase lasts longer than the relative refraction phase. and is 1.2 mls.

In one and the same tissue, the duration of refractoriness changes, especially with functional disorders of the NS or during a disease.

In the trace potential phase, an exaltation phase or a supernormal phase develops, i.e., a strong response arises to actions of any kind. Last in nerve fibers 12-30 mls, in muscles 50 mls or more.

"

Irritability is the general biological ability of cells and organisms to react (respond) to the influence of environmental factors. The most important element in the process of irritability are receptors. Receptor cells are called biological sensors or transducers, as they convert the energy of pressure, light, chemical and other factors into electrical impulses. In plants, receptors are not as differentiated as in animals. They are ectodesmata, starch statoliths, sensitive hairs, etc.

The main forms of manifestation of the irritability of organisms are various types of motor reactions that are carried out by the whole organism or its individual parts. The most common motor reactions of living organisms to changes in environmental conditions are taxis, and in plants (except taxis) - tropisms, nastia, nutations and autonomous movements.

Taxis is the movement of the body, manifested in its spatial movement relative to the stimulus (amoeba, infusoria). If the movement of the organism is carried out in the direction of the acting factor, then such a taxis is called positive; and negative when the movement occurs in the opposite direction.

Taxis are classified according to the type of stimulus. Reaction to action: light - phototaxis, chemical compounds - chemotaxis, temperature - thermotaxis. An example of positive phototaxis is the oriented movement of flagellated unicellular algae (chlamydomonas) to the zone of optimal illumination in an aquarium or pond, the appropriate orientation of chloroplasts in leaf mesophyll cells; chemotaxis - the accumulation of bacterial cells near the dead cell of the ciliate, the movement of leukocytes to the bacterium, etc.

Tropisms are a motor reaction of organs and parts of plants to the unilateral influence of an environmental factor (light, gravity, water, chemicals, etc.).

Depending on the plant organism, tropisms can be positive, when, due to uneven growth, an organ or part of the plant bends towards the acting factor, and negative, when growth processes cause the organ to deviate in the opposite direction. In plants, geotropism is best expressed - the reaction of its individual organs to the unilateral influence of the earth's gravity.

There are three types of geotropism: positive - when the organ grows vertically downwards, negative - when the direction of movement is opposite, and transverse, or diageotropism, when the organ tries to take a horizontal position. The main taproots have, as a rule, positive geotropism; branches of the first order of woody plants, petioles of many leaves - negative; many rhizomes, lateral roots - transverse.

Phototropisms are the growth movements of plants in response to unilateral exposure to light. With unilateral exposure to light (in a clearing, near buildings, in a room, etc.), the phototropism of individual shoots or even the entire above-ground part is especially pronounced. Plants, as it were, are drawn to the light (plants on the windowsill, sunflower inflorescences, leaves on shoots).

Other physical and chemical factors can also have a unilateral effect on growing organs. Accordingly, chemotropisms, hydrotropisms, thermotropisms, magnetotropisms are also distinguished (i.e., the classification of tropisms depends on the source of irritation).

Nastia. To nastic belong movements that are the response of organs or parts of plants to the action of stimuli that do not have a specific direction, but affect diffusely and evenly from different sides. That is why it is impossible to establish any one-sided factor of the motor reaction.

Epinasty - when the bend of an organ (usually a leaf) occurs downward. This may be due to accelerated growth or turgor stretching of the upper side of the petiole (lowering leaves of mimosa, vetch, white locust).

Hyponasia - bending of the organ due to the accelerated growth or stretching of the cells of the lower side of the petiole and the central vein (lifting the leaf blades up at night at the quinoa, tobacco).

Nyctinastia - motor reactions caused by the onset of darkness, the so-called sleep in plants (closing flowers, lowering inflorescences in carrots at night).

Photonastia - opening of flower petals with increased lighting (chicory, dandelion, potato inflorescences).

Thermonastia - opening of the petals when the temperature rises (tulip, coltsfoot, garden poppy).

Seismonasty - the movement of plant organs that are a response to a blow or concussion (mimosa, sour, purslane).

Nutations. Nutations are understood as the ability of plants to circular or pendulum movements due to periodically repeating changes in the values ​​of turgor pressure and the intensity of growth of opposite sides of a certain organ. This is best expressed at the tops and tendrils of climbing plants. In climbing plants, the tip during growth makes uniform nutational movements and, upon contact with the support, begins to wrap around it (hops, pumpkin, peas, beans).