Task 1. Plant adaptation to seed dispersal

Establish how plants adapted to seed dispersal through insects, birds, mammals, and humans. Fill the table.

Plant adaptations for seed dispersal

№ p/p	plant species	Insects	Birds	Mammal nourishing	Man
	cultural
	felt
	tripartite
	forget-me-not
	Burdock ordinary

What properties do the seeds of the plants listed in the table have that contribute to the spread of seeds by the methods you have found? Give specific examples.

The interaction of two populations can theoretically be represented as paired combinations of the symbols "+", "-", "0", where "+" denotes a benefit for the population, "-" - the deterioration of the population, that is, harm, and "0" - the absence significant changes in the interaction. Using the proposed symbolism, define the types of interaction, give examples of relationships and make a table in your notebook.

Biotic relationships

relationships	Symbolic designation	Definition relationships	Examples relationships of this type

1. Using the handout didactic material, make up the food web of the lake ecosystem.

2. Under what conditions will the lake not change for a long time?

3. What actions of people can lead to the rapid destruction of the lake ecosystem?

Individual task for the module "From the ecology of organisms to the ecology of ecosystems" Option 6

Task 1. Adaptation of living organisms to extreme living conditions

Many organisms during their life periodically experience the influence of factors that are very different from the optimum. They have to endure extreme heat, and frosts, and summer droughts, and drying up of water bodies, and lack of food. How do they adapt to such extreme conditions, when normal life is very difficult? Give examples of the main ways of adapting to the transfer of adverse living conditions

Task 2. Biotic relationships.

Determine from the graphs what consequences the relationship between two closely related species of organisms living in the same ecological niche can lead to? What is this relationship called? Explain the answer.

Fig.11. The growth in the number of two types of ciliates-shoes (1 - tailed slipper, 2 - golden slipper):

A - when grown in pure cultures with a large amount of food (bacteria); B - in mixed culture, with the same amount of food

Task 3. Natural ecosystems of the Southern Urals

1. Make up the food web of a river ecosystem.

2. Under what conditions will the river not change for a long time?

3. What actions of people can lead to the rapid destruction of the river ecosystem?

4. Describe the trophic structure of the ecosystem using the ecological pyramids of abundance, biomass, and energy.

in biology, the development of any trait that contributes to the survival of the species and its reproduction. Adaptations can be morphological, physiological, or behavioral.

Morphological adaptations involve changes in the shape or structure of an organism. An example of such an adaptation is the hard shell of turtles, which provides protection from predatory animals. Physiological adaptations are associated with chemical processes in the body. Thus, the smell of a flower can serve to attract insects and thus contribute to the pollination of a plant. Behavioral adaptation is associated with a certain aspect of the animal's life. A typical example is a bear's winter sleep. Most adaptations are a combination of these types. For example, bloodsucking in mosquitoes is provided by a complex combination of such adaptations as the development of specialized parts of the oral apparatus adapted for sucking, the formation of search behavior to find a prey animal, and the production of special secretions by the salivary glands that prevent the blood being sucked from clotting.

All plants and animals are constantly adapting to their environment. To understand how this happens, it is necessary to consider not only the animal or plant as a whole, but also the genetic basis of adaptation.

genetic basis. In each species, the program for the development of traits is embedded in the genetic material. The material and the program encoded in it are passed on from one generation to the next, remaining relatively unchanged, so that representatives of one species or another look and behave almost the same. However, in a population of organisms of any kind, there are always small changes in the genetic material and, therefore, variations in the characteristics of individual individuals. It is from these diverse genetic variations that the process of adaptation selects or favors the development of those traits that most increase the chances of survival and thereby the preservation of genetic material. Adaptation can thus be seen as the process by which genetic material improves its chances of being retained in subsequent generations. From this point of view, each species represents a successful way of preserving a certain genetic material.

In order to pass on genetic material, an individual of any species must be able to feed, survive to a breeding season, leave offspring, and then spread it over as large a territory as possible.

Nutrition. All plants and animals must receive energy and various substances from the environment, primarily oxygen, water and inorganic compounds. Almost all plants use the energy of the sun, transforming it in the process of photosynthesis. (see also PHOTOSYNTHESIS). Animals get energy by eating plants or other animals.

Each species is adapted in a certain way to provide itself with food. Hawks have sharp claws for grasping prey, and the location of their eyes in front of the head allows them to assess the depth of space, which is necessary for hunting when flying at high speed. Other birds, such as herons, have developed long necks and legs. They forage for food by cautiously roaming the shallow waters and lying in wait for gaping aquatic animals. Darwin's finches, a group of closely related bird species from the Galapagos Islands, are a classic example of highly specialized adaptations to different diets. Due to certain adaptive morphological changes, primarily in the structure of the beak, some species became granivorous, while others became insectivorous.

If we turn to fish, then predators, such as sharks and barracudas, have sharp teeth for catching prey. Others, such as small anchovies and herring, obtain small food particles by filtering seawater through comb-shaped gill rakers.

In mammals, an excellent example of adaptation to the type of food are the features of the structure of the teeth. The fangs and molars of leopards and other felines are extremely sharp, which allows these animals to hold and tear the victim's body. In deer, horses, antelopes and other grazing animals, large molars have wide ribbed surfaces, adapted for chewing grass and other plant foods.

A variety of ways to obtain nutrients can be observed not only in animals, but also in plants. Many of them, primarily legumes - peas, clover and others - have developed symbiotic, i.e. mutually beneficial relationship with bacteria: bacteria convert atmospheric nitrogen into a chemical form available to plants, and plants provide energy to bacteria. Insectivorous plants, such as sarracenia and sundew, obtain nitrogen from the bodies of insects caught by trapping leaves.

Protection. The environment consists of living and non-living components. The living environment of any species includes animals that feed on individuals of that species. The adaptations of carnivorous species are geared towards efficient foraging; prey species adapt so as not to become the prey of predators.

Many species - potential prey - have a protective or camouflage coloration that hides them from predators. So, in some species of deer, the spotted skin of young individuals is invisible against the background of alternating spots of light and shadow, and it is difficult to distinguish white hares against the background of snow cover. The long thin bodies of stick insects are also difficult to see because they resemble knots or twigs of bushes and trees.

Deer, hares, kangaroos, and many other animals have evolved long legs to enable them to run away from predators. Some animals, such as opossums and pig-faced snakes, have even developed a peculiar way of behavior - imitation of death, which increases their chances of survival, since many predators do not eat carrion.

Some types of plants are covered with thorns or thorns that scare away animals. Many plants have a disgusting taste to animals.

Environmental factors, in particular climatic ones, often put living organisms in difficult conditions. For example, animals and plants often have to adapt to temperature extremes. Animals escape the cold by using insulating fur or feathers by migrating to warmer climates or hibernating. Most plants survive the cold by going into a state of dormancy, equivalent to hibernation in animals.

In hot weather, the animal is cooled by sweating or frequent breathing, which increases evaporation. Some animals, especially reptiles and amphibians, are able to hibernate in summer, which is essentially the same as winter hibernation, but caused by heat rather than cold. Others are just looking for a cool place.

Plants can maintain their temperature to some extent by regulating the rate of evaporation, which has the same cooling effect as perspiration in animals.

Reproduction. A critical step in ensuring the continuity of life is reproduction, the process by which genetic material is passed on to the next generation. Reproduction has two important aspects: the meeting of heterosexual individuals for the exchange of genetic material and the rearing of offspring.

Among the adaptations that ensure the meeting of individuals of different sexes is sound communication. In some species, the sense of smell plays an important role in this sense. For example, cats are strongly attracted to the smell of a cat in estrus. Many insects secrete the so-called. attractants - chemicals that attract individuals of the opposite sex. Flower scents are effective plant adaptations to attract pollinating insects. Some flowers are sweet-smelling and attract nectar-feeding bees; others smell disgusting, attracting carrion flies.

Vision is also very important for meeting individuals of different sexes. In birds, the mating behavior of the male, his lush feathers and bright coloring, attracts the female and prepares her for copulation. Flower color in plants often indicates which animal is needed to pollinate that plant. For example, flowers pollinated by hummingbirds are colored red, which attracts these birds.

Many animals have developed ways to protect their offspring during the initial period of life. Most adaptations of this kind are behavioral and involve actions by one or both parents that increase the chances of survival of the young. Most birds build nests specific to each species. However, some species, such as the cowbird, lay their eggs in the nests of other bird species and entrust the young to the parental care of the host species. Many birds and mammals, as well as some fish, have a period when one of the parents takes great risks, taking on the function of protecting offspring. Although this behavior sometimes threatens the death of the parent, it ensures the safety of the offspring and the preservation of the genetic material.

A number of species of animals and plants use a different reproduction strategy: they produce a huge number of offspring and leave them unprotected. In this case, the low chances of survival for an individual growing individual are balanced by the large number of offspring. see also REPRODUCTION.

Resettlement. Most species have developed mechanisms for removing offspring from the places where they were born. This process, called dispersal, increases the likelihood that offspring will grow up in an unoccupied territory.

Most animals simply avoid places where there is too much competition. However, evidence is accumulating that dispersal is due to genetic mechanisms.

Many plants have adapted to seed dispersal with the help of animals. So, cocklebur seedlings have hooks on the surface, with which they cling to the hair of animals passing by. Other plants produce tasty fleshy fruits, such as berries, which are eaten by animals; the seeds pass through the digestive tract and are "sown" intact elsewhere. Plants also use the wind to propagate. For example, the "propellers" of maple seeds are carried by the wind, as well as the seeds of the cottonwort, which have tufts of fine hairs. Steppe plants of the tumbleweed type, which acquire a spherical shape by the time the seeds ripen, are distilled by the wind over long distances, dispersing the seeds along the way.

The above were just some of the most striking examples of adaptations. However, almost every sign of any species is the result of adaptation. All these signs make up a harmonious combination, which allows the body to successfully lead its special way of life. Man in all his attributes, from the structure of the brain to the shape of the big toe, is the result of adaptation. Adaptive traits contributed to the survival and reproduction of his ancestors who had the same traits. In general, the concept of adaptation is of great importance for all areas of biology. see also HEREDITY.

LITERATURE Levontin R.K. Adaptation. – In: Evolution. M., 1981

You receive plants with ACS, the root system of plants is packed in a plastic bag with coconut fiber, which allows the root system not to dry out and not to overmoisten. Succulent plants are transmitted with ACS.

So, you brought the plants home. What's next?

Adaptation.

The plant must be inspected and removed (if found) all necrotic tissue, including dead roots. Further, the plants should be treated with a systemic fungicide (foundazol and its analogues) and an insecticide, even if there are no visual signs of infection and the presence of pests. Remember, any plant that enters your home can be infested by pests without showing visual signs of damage. Regardless of where you got the plant - from a neighbor, in a store, bought from a collector, in greenhouses or nurseries - the first thing you should do is treat it preventively from pests and fungic diseases.

Fusarium rot pose a serious threat to non-adapted plants, they are not known to be treated, they can only be stopped with a systemic fungicide. Available in Russia - systemic (benlat, benomyl) or contact (fludioxonil). Rot pathogens can either be carried by insects, be in the soil in which you plant the plant, or already be dormant in the plant, since absolutely all soils are infected with fusarium, including in Thailand. As long as the plant is healthy, has a stable set of standard reactions of a healthy plant to external stimuli, it is able to resist pathogens, but under stress (moving, flooding, temperature fluctuations, etc.), dormant diseases actively develop and can destroy the plant in less than a day. Planting in inert soil (such as coconut) does not provide a guarantee, but significantly reduces the likelihood of disease development.

It makes sense to fight both pests and rot at the same time, since insects and mites can carry diseases from plant to plant.

About Fusarium rot and pest control I personally had a conversation back in 2009 with the Head of the Plant Protection Department of the Main Botanical Garden L.Yu.Treivas, the results of this conversation are taken into account in the following recommendations:

1. For the treatment of newly arrived plants, you can use a tank mixture:

"Fundazol" (20g) + "Hom" (40g) + "Aktellik" (20g) per 10 liters of water (20g = 1 tablespoon).

I do not recommend soaking unadapted plants , the treatment must be carried out by spraying. I would like to remind you that the treatment should be carried out with all precautions - a mask, glasses, gloves - and, of course, in the absence of children and animals. The same "Aktellik" is very harmful to humans. However, it is no more harmful than Fitoverma, which is positioned as a drug of biological origin (look at its hazard class). At the moment, in our market, Actellik from Syngenta (aka pirimiphos) is one of the most advanced, both in terms of effectiveness (it has been used relatively recently, and resistance to it has not yet been developed), and in terms of safety for humans. It has relatively low toxicity (so much so that it can be used in household mosquito sprays). I note that until safe chemicals have been invented in the world, neither pesticides nor fungicides, and we will have to put up with this, alas, for some reason the tick does not want to die from the smell of roses.

I strongly do not recommend washing the root system, this will lead to waterlogging and injury to the roots, and as a result, an avalanche-like development of necrosis of the root system and death of the plant. Even if you have heard enough advice from "experienced" people on any forums or groups who advise you to shake off all the old soil and then thoroughly wash the root system, do not listen to them, they do not understand what they advise. Plants are already in a state of stress, their main task at this stage is to make the root system work in new conditions, and the less you injure healthy roots, the greater the chance of success.

2. After the plant has successfully adapted, it is necessary to carry out a set of preventive measures:

• a single spill of the soil with the tank mixture "Fundazol" (20g / 10 l) + "Aktellik" (according to the instructions). L.Yu. Treivas suggests doing this on an ongoing basis twice a year, but I am against it, in my opinion, such frequent use leads to the formation of populations of pathogens and pests that are resistant to chemicals.
• spraying with the same mixture 2 times a year (autumn / winter).

I do not recommend increasing the dosage of drugs on your own, if you do not have a specialized biological or chemical education. Do not forget about such a thing as phytotoxicity, a plant may die from an abundance of chemistry.

Same way, I don't recommend making your own tank mixes. M You can, of course, until the end of time make crazy tank mixes from ingredients that either duplicate or mutually exclude each other and experiment on your plants based on your subjective feelings. But if we are interested in the result, and not the process, it is still better to be based on the opinion of professionals, choosing for yourself what is clearer, more accessible and more real to you.

3. Disinfection of pots before planting:

soaking in 1% solution of potassium permanganate, or in "Fundazol" (40g / 10l of water).

Brief overview of other chemicals(acaricides and fungicides):

1. Instead of Actellik, you can use Fufanon (in fact, it is, in fact, karbofos, only much better purified from toxins harmful to humans), both drugs are systemic acaricides and act on all stages of development, except eggs. I draw your attention to the fact that, according to L.Yu. Treivas, there are no drugs that act on tick eggs at the moment. It is even better to alternate these drugs - 2 treatments with Actellik, 2 treatments with Fufanon. Personally, I love the tank mixture "Confidor" + "Fundazol" in the dosages indicated on the manufacturer's packaging.

3. All fungicides commercially available in our country are not systemic, except for "Fundazol" and therefore are not suitable for combating Fusarium, which spreads through the vascular system of the plant. Unfortunately, at the moment we do not have an alternative to Fundazol.

4. "Fitosporin" and similar preparations based on the action of microbiology, despite the wide spectrum of action declared in the annotation, work only for preventive treatment of seeds.

5. "Sunmite" is effective, has only a contact effect, the plants must be treated very carefully, since any untreated area is completely unprotected. It can act on eggs if it gets directly on them or pupae, the solution penetrates inside and partially enters the developing organism. The toxicity of the drug is low, it decomposes very quickly in the environment with water and light, and does not accumulate in water and soil. Drugs of this class (blockers of cellular respiration) very quickly cause resistance, therefore, a strict restriction is imposed on the use, they can be used no more than 2 times a season.

What not to do:

1. Soak plants in various stimulating solutions, even if these solutions work well in your conditions on other plants. Unadapted plants can react to soaking with a reset of the root system and an avalanche-like development of rot. When using various stimulants, an unadapted plant, instead of adjusting its response system to changing environmental conditions, will respond to the stimulation of a process that is not a priority for it at this stage, and it will not have any left for a process that is vitally important. resources. In my opinion, it is extremely dangerous to spur processes in unadapted plants, let the plant independently establish a system of responses to external signals, providing it with the required conditions for adaptation. Since the main thing that a plant must do is to build up a working root system that can ensure the vital activity of the entire plant organism, the use of root formation hormones based on heteroauxin is permissible, but only in the form of spraying. Pro plant immunity can be read here .
2. Plants should not be shared with those already living in the house, they should be quarantined in a separate greenhouse. You should not place plants in outdoor unheated greenhouses - in the summer at night in Moscow and the region around + 15C, in the greenhouse, of course, the temperature is higher, but the differences in day and night temperatures are quite significant, and plants now need an even temperature regime around + 30C.

hothouse- a container with a lid, holes 0.5 cm in diameter in 10 cm increments were made in the lid over the entire area for ventilation, if the greenhouse is large enough, additional ventilation is not required. If the volume of air in the greenhouse is small, or the plants stand too tightly in it, ventilation is mandatory.

Cellophane bag for the head(when only the ground part of the plant is inside the package) totally unsuitable trying to create increased humidity around the crown in this way, you completely deprive the plant of the movement of air masses, which means you provoke rot, which on non-adapted plants can lead to lightning-fast development of rot.

If there is no greenhouse and is not expected, you can try to take a large bag that fits the whole plant together with the pot- temperature and humidity conditions should be uniform around the entire plant, including the root system. Do not forget that this principle of replacing a greenhouse can be used for a short time, 2-4 days, this is an emergency option, while you get a greenhouse, but it cannot be a full-fledged replacement for a greenhouse for the adaptation period. A microclimate favorable for the development of pathogens is created inside the bag, it is a kind of Petri dish - it is warm, humid, there is no access to fresh air. Remember that with a bag instead of a greenhouse, you can do more harm than good. While the plant is in the bag, air it several times a day.

Before placing the plant in a greenhouse and in the process of adaptation necrotic tissue should be trimmed to healthy tissue. If they are left, the rot will spread further and the weakened plant may die. Until new roots grow to provide nutrition to the vegetative mass, the plant may shed its leaves, this is a normal adaptation process. For trimming, we use sharp scissors or secateurs pre-treated with alcohol, the cut can be powdered with foundation.

Recommended primer for the adaptation period - pure coconut fiber without additives and fertilizers, or perlite, if you like it more. All industrial soils contain organic matter from fields with pathogens of Fusarium rot, which do not pose a serious danger to healthy adapted plants, but carry a serious threat to weakened, unadapted plants. I am often asked the question of how to disinfect the soil. Alas, the causative agents of Fusarium rot are resistant to low temperatures; it makes no sense to freeze the soil. Some incompetent authors suggest steaming the soil before planting. However, they do not take into account the fact that soil disinfection is a double-edged sword, of course, pathogenic flora and fauna will die, but beneficial organisms will die along with it. The earth is a living organism, a complex biocenosis, if it is disturbed, and if it is steamed, sterilized, then soon the soil will again be populated, and, naturally, pathogens will be the first to come to an empty place. In addition, steaming irreparably damages the structure of the soil, it ceases to be hygroscopic and breathable, after some time such soil is sintered into a monolith and becomes completely unsuitable for growing plants. A single spill will be good, a regular spill will lead to the formation of a fungicide-resistant population, so you should not get carried away with regular soil spills with insecticides and fungicides.

Landing it makes sense to use transparent pots (if the plant is large) or disposable cups (the volume depends on the size of the plant). This is necessary for visual monitoring of soil moisture and the formation of new roots. I want to separately draw attention to the fact that the size of the pot should be commensurate with the root system of the plant, you can not take the pot for growth, this will provoke acidification of the soil and the development of rot of the root system.

Watering - be careful with watering, the root system of plants is not yet working, and they can respond to abundant watering with instant avalanche-like decay. Rots are not only wet, but also dry, the plant suddenly dries out, you think that this is from insufficient watering, but in fact, this drying is caused by the development of dry rots. In the clinical picture on a plant with Fusarium, there are both dry leaves and watery ones, and this does not depend on high humidity. With fusarium wilt, the damage and death of plants occur due to a sharp violation of vital functions due to blockage of blood vessels by the mycelium of the fungus and the release of toxic substances (fusaric acid, lycomarasmin, etc.), blockage of blood vessels leads to symptoms of wilting (clinical picture - dry leaves), and toxins cause toxicosis, and it can be expressed precisely in the wateriness of plant leaves. Toxins cause the decomposition of leaf cells, and during decomposition, of course, the picture is not at all dry. Remember that a plant that is slightly overdried has every chance to recover with careful watering, a flooded plant has no chance of recovery.

If the plant is too large and does not fit in a container with a lid, you can build a greenhouse from two containers. The volume of air inside such a greenhouse is sufficient so as not to make additional ventilation holes. If the walls of the greenhouse fog up, it means that ventilation is still necessary, for this the upper container must be moved to provide air access through the gaps formed.

Backlight- an important point for the period of adaptation of the plant, if it is far from a natural light source, or the plant came to you in the autumn-winter period. You can read about the specifics of buying Thai plants in the autumn-winter period here. The backlight should be at least 12 hours a day, among other things, the use of lamps will help provide the plants with the heat they need. During the adaptation period, it is very important to maintain an even temperature regime without daily fluctuations, if this is not possible, the difference between day and night temperatures should be within 5 degrees.

succulent plants(including adeniums), in no case should be placed in a greenhouse, they do not need high humidity, moreover, with high humidity they will be susceptible to rot. Heat, lighting and treatment with fungicide and insecticide for the period of adaptation are, of course, necessary for them. You can highlight succulents for the first 2-3 weeks up to 18 hours a day.

However, I want to warn you against excessive zeal in organizing lighting, plants are contraindicated for light around the clock, they must necessarily have a change of day and night, since at night very important chemical processes take place in plant tissues, the violation of which can lead to the fact that the plant will not be able to develop properly.

Different groups of plants adapt at different times, it happens that after a week new roots appear, and after a couple of weeks new leaves peck, and it happens that the plant sits for months without visible movement ... This, of course, also depends on the season, in the autumn-winter period the plants are at rest and they build up the root system, and they are in no hurry with the vegetative mass. Do not worry, everything has its time, spring will come, and the plant will wake up.

Specifics of Thai agricultural technology adapted plants do not exist. It does not matter where you purchased the plant, what is the country of origin of the planting material, whether it is a Dutch plant, Russian or Thai, it all depends on the needs of a particular culture, there are no general recommendations and cannot be. I am planning a series of articles on agricultural technology of different groups of plants, the articles can be found in the section .

When can we consider that the adaptation process is completed? If you see through the transparent walls of the container in which the plant is planted, new roots, then the plant can begin to be accustomed to life outside the greenhouse. This should be done gradually, removing the lid from the container for short periods of time, gradually increasing the time the plants spend in conditions of low air humidity. Do not rush to pull the plants out of the greenhouses, do it only when you make sure that the leaves do not lose turgor when they are outside the greenhouse, the plant does not slow down the vegetation process, but continues the growth started in the greenhouse, actively builds up the root system and vegetates, and then it, rearranged for permanent residence (for example, a window sill), will not bring you unpleasant surprises in the form of sudden withering and death, but will delight you for many years. It is possible to transplant a plant only when the roots are braided with an earthen ball. Until then, after the acclimatization period is over, simply add granular fertilizers to the coco soil, or use liquid fertilizers if you prefer. Now you can use any stimulants you like.

The adaptability of plant ontogenesis to environmental conditions is the result of their evolutionary development (variability, heredity, selection). During the phylogenesis of each plant species, in the process of evolution, certain needs of the individual for the conditions of existence and adaptability to the ecological niche he occupies have been developed. Moisture and shade tolerance, heat resistance, cold resistance and other ecological features of specific plant species have been formed in the course of evolution as a result of long-term exposure to appropriate conditions. So, heat-loving plants and plants of a short day are characteristic of the southern latitudes, less demanding for heat and plants of a long day - for the northern ones.

In nature, in one geographical region, each plant species occupies an ecological niche corresponding to its biological characteristics: moisture-loving - closer to water bodies, shade-tolerant - under the forest canopy, etc. The heredity of plants is formed under the influence of certain environmental conditions. The external conditions of plant ontogenesis are also important.

In most cases, plants and crops (plantings) of agricultural crops, experiencing the action of certain adverse factors, show resistance to them as a result of adaptation to the conditions of existence that have developed historically, which was noted by K. A. Timiryazev.

1. Basic living environments.

When studying the environment (the habitat of plants and animals and human production activities), the following main components are distinguished: the air environment; aquatic environment (hydrosphere); fauna (human, domestic and wild animals, including fish and birds); flora (cultivated and wild plants, including those growing in water); soil (vegetation layer); subsoil (upper part of the earth's crust, within which mining is possible); climatic and acoustic environment.

The air environment can be external, in which most people spend a smaller part of their time (up to 10-15%), internal production (a person spends up to 25-30% of their time in it) and internal residential, where people stay most of the time (up to 60 -70% or more).

Outside air at the earth's surface contains by volume: 78.08% nitrogen; 20.95% oxygen; 0.94% inert gases and 0.03% carbon dioxide. At an altitude of 5 km, the oxygen content remains the same, while nitrogen increases to 78.89%. Often the air near the surface of the earth has various impurities, especially in cities: there it contains more than 40 ingredients that are alien to the natural air environment. Indoor air in dwellings, as a rule, has

increased content of carbon dioxide, and the internal air of industrial premises usually contains impurities, the nature of which is determined by the production technology. Among the gases, water vapor is released, which enters the atmosphere as a result of evaporation from the Earth. Most of it (90%) is concentrated in the lowest five-kilometer layer of the atmosphere, with height its amount decreases very quickly. The atmosphere contains a lot of dust that gets there from the surface of the Earth and partly from space. During strong waves, the winds pick up water spray from the seas and oceans. This is how salt particles get into the atmosphere from the water. As a result of volcanic eruptions, forest fires, industrial facilities, etc. air is polluted by products of incomplete combustion. Most of all dust and other impurities are in the ground layer of air. Even after rain, 1 cm contains about 30 thousand dust particles, and in dry weather there are several times more of them in dry weather.

All these tiny impurities affect the color of the sky. Molecules of gases scatter the short-wavelength part of the spectrum of the sun's beam, i.e. purple and blue rays. So during the day the sky is blue. And impurity particles, which are much larger than gas molecules, scatter light rays of almost all wavelengths. Therefore, when the air is dusty or contains water droplets, the sky becomes whitish. At high altitudes, the sky is dark purple and even black.

As a result of the photosynthesis taking place on Earth, vegetation annually forms 100 billion tons of organic substances (about half is accounted for by the seas and oceans), while assimilating about 200 billion tons of carbon dioxide and releasing about 145 billion tons into the environment. free oxygen, it is believed that due to photosynthesis, all the oxygen in the atmosphere is formed. The role of green spaces in this cycle is indicated by the following data: 1 hectare of green spaces, on average, purifies the air from 8 kg of carbon dioxide per hour (200 people emitted during this time when breathing). An adult tree releases 180 liters of oxygen per day, and in five months (from May to September) it absorbs about 44 kg of carbon dioxide.

The amount of oxygen released and carbon dioxide absorbed depends on the age of green spaces, species composition, planting density and other factors.

Equally important are marine plants - phytoplankton (mainly algae and bacteria), which release oxygen through photosynthesis.

The aquatic environment includes surface and ground waters. Surface waters are mainly concentrated in the ocean, with a content of 1 billion 375 million cubic kilometers - about 98% of all water on Earth. The surface of the ocean (water area) is 361 million square kilometers. It is about 2.4 times the land area - a territory that occupies 149 million square kilometers. The water in the ocean is salty, and most of it (more than 1 billion cubic kilometers) retains a constant salinity of about 3.5% and a temperature of about 3.7 ° C. Noticeable differences in salinity and temperature are observed almost exclusively in the surface layer of water, and also in the marginal and especially in the Mediterranean seas. The content of dissolved oxygen in water decreases significantly at a depth of 50-60 meters.

Groundwater can be saline, brackish (lower salinity) and fresh; existing geothermal waters have an elevated temperature (more than 30ºC).

For the production activities of mankind and its household needs, fresh water is required, the amount of which is only 2.7% of the total volume of water on Earth, and a very small share of it (only 0.36%) is available in places that are easily accessible for extraction. Most of the fresh water is found in snow and freshwater icebergs found in areas primarily in the Antarctic Circle.

The annual global river runoff of fresh water is 37.3 thousand cubic kilometers. In addition, a part of groundwater equal to 13 thousand cubic kilometers can be used. Unfortunately, most of the river flow in Russia, amounting to about 5,000 cubic kilometers, falls on the marginal and sparsely populated northern territories.

The climatic environment is an important factor determining the development of various species of flora and fauna and its fertility. A characteristic feature of Russia is that most of its territory has a much colder climate than in other countries.

All considered components of the environment are included in

BIOSPHERE: the shell of the Earth, including part of the atmosphere, the hydrosphere and the upper part of the lithosphere, which are interconnected by complex biochemical cycles of matter and energy migration, the geological shell of the Earth, inhabited by living organisms. The upper limit of the life of the biosphere is limited by the intense concentration of ultraviolet rays; lower - high temperature of the earth's interior (over 100`C). Its extreme limits are reached only by lower organisms - bacteria.

Adaptation (adaptation) of a plant to specific environmental conditions is ensured by physiological mechanisms (physiological adaptation), and in a population of organisms (species) - due to the mechanisms of genetic variability, heredity and selection (genetic adaptation). Environmental factors can change regularly and randomly. Regularly changing environmental conditions (change of seasons) develop in plants genetic adaptation to these conditions.

In the natural conditions of growth or cultivation of a species, in the course of their growth and development, they often experience the influence of adverse environmental factors, which include temperature fluctuations, drought, excessive moisture, soil salinity, etc. Each plant has the ability to adapt to changing conditions. environmental conditions within the limits determined by its genotype. The higher the ability of a plant to change metabolism in accordance with the environment, the wider the reaction rate of this plant and the better the ability to adapt. This property distinguishes resistant varieties of agricultural crops. As a rule, slight and short-term changes in environmental factors do not lead to significant disturbances in the physiological functions of plants, which is due to their ability to maintain a relatively stable state under changing environmental conditions, i.e., to maintain homeostasis. However, sharp and prolonged impacts lead to disruption of many functions of the plant, and often to its death.

Under the influence of unfavorable conditions, the decrease in physiological processes and functions can reach critical levels that do not ensure the implementation of the genetic program of ontogenesis, energy metabolism, regulatory systems, protein metabolism and other vital functions of the plant organism are disrupted. When a plant is exposed to unfavorable factors (stressors), a stressed state arises in it, a deviation from the norm - stress. Stress is a general non-specific adaptive reaction of the body to the action of any adverse factors. There are three main groups of factors that cause stress in plants: physical - insufficient or excessive humidity, light, temperature, radioactive radiation, mechanical stress; chemical - salts, gases, xenobiotics (herbicides, insecticides, fungicides, industrial waste, etc.); biological - damage by pathogens or pests, competition with other plants, the influence of animals, flowering, fruit ripening.

The adaptability of plant ontogenesis to environmental conditions is the result of their evolutionary development (variability, heredity, selection). During the phylogenesis of each plant species, in the process of evolution, certain needs of the individual for the conditions of existence and adaptability to the ecological niche he occupies have been developed. Moisture and shade tolerance, heat resistance, cold resistance and other ecological features of specific plant species have been formed in the course of evolution as a result of long-term exposure to appropriate conditions. So, heat-loving plants and plants of a short day are characteristic of the southern latitudes, less demanding for heat and plants of a long day - for the northern ones.

In nature, in one geographical region, each plant species occupies an ecological niche corresponding to its biological characteristics: moisture-loving - closer to water bodies, shade-tolerant - under the forest canopy, etc. The heredity of plants is formed under the influence of certain environmental conditions. The external conditions of plant ontogenesis are also important.

In most cases, plants and crops (plantings) of agricultural crops, experiencing the action of certain adverse factors, show resistance to them as a result of adaptation to the conditions of existence that have developed historically, which was noted by K. A. Timiryazev.

1. Basic living environments.

When studying the environment (the habitat of plants and animals and human production activities), the following main components are distinguished: the air environment; aquatic environment (hydrosphere); fauna (human, domestic and wild animals, including fish and birds); flora (cultivated and wild plants, including those growing in water); soil (vegetation layer); subsoil (upper part of the earth's crust, within which mining is possible); climatic and acoustic environment.

The air environment can be external, in which most people spend a smaller part of their time (up to 10-15%), internal production (a person spends up to 25-30% of their time in it) and internal residential, where people stay most of the time (up to 60 -70% or more).

Outside air at the earth's surface contains by volume: 78.08% nitrogen; 20.95% oxygen; 0.94% inert gases and 0.03% carbon dioxide. At an altitude of 5 km, the oxygen content remains the same, while nitrogen increases to 78.89%. Often the air near the surface of the earth has various impurities, especially in cities: there it contains more than 40 ingredients that are alien to the natural air environment. Indoor air in dwellings, as a rule, has

increased content of carbon dioxide, and the internal air of industrial premises usually contains impurities, the nature of which is determined by the production technology. Among the gases, water vapor is released, which enters the atmosphere as a result of evaporation from the Earth. Most of it (90%) is concentrated in the lowest five-kilometer layer of the atmosphere, with height its amount decreases very quickly. The atmosphere contains a lot of dust that gets there from the surface of the Earth and partly from space. During strong waves, the winds pick up water spray from the seas and oceans. This is how salt particles get into the atmosphere from the water. As a result of volcanic eruptions, forest fires, industrial facilities, etc. air is polluted by products of incomplete combustion. Most of all dust and other impurities are in the ground layer of air. Even after rain, 1 cm contains about 30 thousand dust particles, and in dry weather there are several times more of them in dry weather.

All these tiny impurities affect the color of the sky. Molecules of gases scatter the short-wavelength part of the spectrum of the sun's beam, i.e. purple and blue rays. So during the day the sky is blue. And impurity particles, which are much larger than gas molecules, scatter light rays of almost all wavelengths. Therefore, when the air is dusty or contains water droplets, the sky becomes whitish. At high altitudes, the sky is dark purple and even black.

As a result of the photosynthesis taking place on Earth, vegetation annually forms 100 billion tons of organic substances (about half is accounted for by the seas and oceans), while assimilating about 200 billion tons of carbon dioxide and releasing about 145 billion tons into the environment. free oxygen, it is believed that due to photosynthesis, all the oxygen in the atmosphere is formed. The role of green spaces in this cycle is indicated by the following data: 1 hectare of green spaces, on average, purifies the air from 8 kg of carbon dioxide per hour (200 people emitted during this time when breathing). An adult tree releases 180 liters of oxygen per day, and in five months (from May to September) it absorbs about 44 kg of carbon dioxide.

The amount of oxygen released and carbon dioxide absorbed depends on the age of green spaces, species composition, planting density and other factors.

Equally important are marine plants - phytoplankton (mainly algae and bacteria), which release oxygen through photosynthesis.

The aquatic environment includes surface and ground waters. Surface waters are mainly concentrated in the ocean, with a content of 1 billion 375 million cubic kilometers - about 98% of all water on Earth. The surface of the ocean (water area) is 361 million square kilometers. It is about 2.4 times the land area - a territory that occupies 149 million square kilometers. The water in the ocean is salty, and most of it (more than 1 billion cubic kilometers) retains a constant salinity of about 3.5% and a temperature of about 3.7 ° C. Noticeable differences in salinity and temperature are observed almost exclusively in the surface layer of water, and also in the marginal and especially in the Mediterranean seas. The content of dissolved oxygen in water decreases significantly at a depth of 50-60 meters.

Groundwater can be saline, brackish (lower salinity) and fresh; existing geothermal waters have an elevated temperature (more than 30ºC).

For the production activities of mankind and its household needs, fresh water is required, the amount of which is only 2.7% of the total volume of water on Earth, and a very small share of it (only 0.36%) is available in places that are easily accessible for extraction. Most of the fresh water is found in snow and freshwater icebergs found in areas primarily in the Antarctic Circle.

The annual global river runoff of fresh water is 37.3 thousand cubic kilometers. In addition, a part of groundwater equal to 13 thousand cubic kilometers can be used. Unfortunately, most of the river flow in Russia, amounting to about 5,000 cubic kilometers, falls on the marginal and sparsely populated northern territories.

The climatic environment is an important factor determining the development of various species of flora and fauna and its fertility. A characteristic feature of Russia is that most of its territory has a much colder climate than in other countries.

All considered components of the environment are included in

BIOSPHERE: the shell of the Earth, including part of the atmosphere, the hydrosphere and the upper part of the lithosphere, which are interconnected by complex biochemical cycles of matter and energy migration, the geological shell of the Earth, inhabited by living organisms. The upper limit of the life of the biosphere is limited by the intense concentration of ultraviolet rays; lower - high temperature of the earth's interior (over 100`C). Its extreme limits are reached only by lower organisms - bacteria.

Adaptation (adaptation) of a plant to specific environmental conditions is ensured by physiological mechanisms (physiological adaptation), and in a population of organisms (species) - due to the mechanisms of genetic variability, heredity and selection (genetic adaptation). Environmental factors can change regularly and randomly. Regularly changing environmental conditions (change of seasons) develop in plants genetic adaptation to these conditions.

In the natural conditions of growth or cultivation of a species, in the course of their growth and development, they often experience the influence of adverse environmental factors, which include temperature fluctuations, drought, excessive moisture, soil salinity, etc. Each plant has the ability to adapt to changing conditions. environmental conditions within the limits determined by its genotype. The higher the ability of a plant to change metabolism in accordance with the environment, the wider the reaction rate of this plant and the better the ability to adapt. This property distinguishes resistant varieties of agricultural crops. As a rule, slight and short-term changes in environmental factors do not lead to significant disturbances in the physiological functions of plants, which is due to their ability to maintain a relatively stable state under changing environmental conditions, i.e., to maintain homeostasis. However, sharp and prolonged impacts lead to disruption of many functions of the plant, and often to its death.

Under the influence of unfavorable conditions, the decrease in physiological processes and functions can reach critical levels that do not ensure the implementation of the genetic program of ontogenesis, energy metabolism, regulatory systems, protein metabolism and other vital functions of the plant organism are disrupted. When a plant is exposed to unfavorable factors (stressors), a stressed state arises in it, a deviation from the norm - stress. Stress is a general non-specific adaptive reaction of the body to the action of any adverse factors. There are three main groups of factors that cause stress in plants: physical - insufficient or excessive humidity, light, temperature, radioactive radiation, mechanical stress; chemical - salts, gases, xenobiotics (herbicides, insecticides, fungicides, industrial waste, etc.); biological - damage by pathogens or pests, competition with other plants, the influence of animals, flowering, fruit ripening.

The strength of stress depends on the rate of development of an unfavorable situation for the plant and the level of the stress factor. With the slow development of unfavorable conditions, the plant adapts better to them than with a short-term but strong effect. In the first case, as a rule, specific mechanisms of resistance are manifested to a greater extent, in the second - non-specific ones.

Under unfavorable natural conditions, the resistance and productivity of plants are determined by a number of signs, properties, and protective and adaptive reactions. Various plant species provide stability and survival in adverse conditions in three main ways: through mechanisms that allow them to avoid adverse effects (dormancy, ephemera, etc.); through special structural devices; due to physiological properties that allow them to overcome the harmful effects of the environment.

Annual agricultural plants in temperate zones, completing their ontogeny in relatively favorable conditions, overwinter in the form of stable seeds (dormancy). Many perennial plants overwinter as underground storage organs (bulbs or rhizomes) protected from freezing by a layer of soil and snow. Fruit trees and shrubs of temperate zones, protecting themselves from the winter cold, shed their leaves.

Protection from adverse environmental factors in plants is provided by structural adaptations, features of the anatomical structure (cuticle, crust, mechanical tissues, etc.), special protective organs (burning hairs, spines), motor and physiological reactions, and the production of protective substances (resins, phytoncides , toxins, protective proteins).

Structural adaptations include small-leaved and even the absence of leaves, a waxy cuticle on the surface of leaves, their dense omission and immersion of stomata, the presence of succulent leaves and stems that retain water reserves, erectoid or drooping leaves, etc. Plants have various physiological mechanisms that allow them to adapt to unfavorable conditions. environmental conditions. This is a self-type of photosynthesis in succulent plants, minimizing water loss and essential for the survival of plants in the desert, etc.

2. Adaptation in plants

Cold tolerance of plants

Plant resistance to low temperatures is divided into cold resistance and frost resistance. Cold resistance is understood as the ability of plants to tolerate positive temperatures slightly higher than 0 C. Cold resistance is characteristic of plants of the temperate zone (barley, oats, flax, vetch, etc.). Tropical and subtropical plants are damaged and die at temperatures from 0º to 10º C (coffee, cotton, cucumber, etc.). For the majority of agricultural plants, low positive temperatures are not harmful. This is due to the fact that during cooling, the enzymatic apparatus of plants is not upset, resistance to fungal diseases does not decrease, and no noticeable damage to plants occurs at all.

The degree of cold resistance of different plants is not the same. Many plants of southern latitudes are damaged by cold. At a temperature of 3 ° C, cucumber, cotton, beans, corn, and eggplant are damaged. Varieties vary in cold tolerance. To characterize the cold resistance of plants, the concept of the temperature minimum at which plant growth stops is used. For a large group of agricultural plants, its value is 4 °C. However, many plants have a higher temperature minimum and therefore are less resistant to cold.

Adaptation of plants to low positive temperatures.

Resistance to low temperatures is a genetically determined trait. The cold resistance of plants is determined by the ability of plants to maintain the normal structure of the cytoplasm, to change the metabolism during the period of cooling and the subsequent increase in temperature at a sufficiently high level.

Frost resistance of plants

Frost resistance - the ability of plants to tolerate temperatures below 0 ° C, low negative temperatures. Frost-resistant plants are able to prevent or reduce the effect of low negative temperatures. Frosts in winter with temperatures below -20 ° C are common for a significant part of the territory of Russia. Annual, biennial and perennial plants are exposed to frost. Plants endure winter conditions in different periods of ontogeny. In annual crops, seeds (spring plants), sprouted plants (winter crops) overwinter, in biennial and perennial crops - tubers, root crops, bulbs, rhizomes, adult plants. The ability of winter, perennial herbaceous and woody fruit crops to overwinter is due to their rather high frost resistance. The tissues of these plants may freeze, but the plants do not die.

Freezing of plant cells and tissues and the processes occurring during this.

The ability of plants to tolerate negative temperatures is determined by the hereditary basis of a given plant species, however, the frost resistance of one and the same plant depends on the conditions preceding the onset of frost, affecting the nature of ice formation. Ice can form both in the cell protoplast and in the intercellular space. Not all ice formation causes plant cells to die.

A gradual decrease in temperature at a rate of 0.5-1 °C/h leads to the formation of ice crystals, primarily in the intercellular spaces, and initially do not cause cell death. However, the consequences of this process can be detrimental to the cell. The formation of ice in the protoplast of the cell, as a rule, occurs with a rapid decrease in temperature. Coagulation of protoplasmic proteins occurs, cell structures are damaged by ice crystals formed in the cytosol, cells die. Plants killed by frost after thawing lose turgor, water flows out of their fleshy tissues.

Frost-resistant plants have adaptations that reduce cell dehydration. With a decrease in temperature in such plants, an increase in the content of sugars and other substances that protect tissues (cryoprotectors) is noted, these are primarily hydrophilic proteins, mono- and oligosaccharides; decrease in cell hydration; an increase in the amount of polar lipids and a decrease in the saturation of their fatty acid residues; an increase in the number of protective proteins.

The degree of frost resistance of plants is greatly influenced by sugars, growth regulators and other substances formed in the cells. In overwintering plants, sugars accumulate in the cytoplasm, and the starch content decreases. The influence of sugars on increasing the frost resistance of plants is multifaceted. Accumulation of sugars prevents freezing of a large volume of intracellular water, significantly reduces the amount of ice formed.

The property of frost resistance is formed in the process of plant ontogenesis under the influence of certain environmental conditions in accordance with the plant genotype, associated with a sharp decrease in growth rates, the transition of the plant to a dormant state.

The life cycle of development of winter, biennial and perennial plants is controlled by the seasonal rhythm of light and temperature periods. Unlike spring annuals, they begin to prepare to endure adverse winter conditions from the moment they stop growing and then during the fall when temperatures drop.

Winter hardiness of plants

Winter hardiness as resistance to a complex of unfavorable overwintering factors.

The direct effect of frost on cells is not the only danger that threatens perennial herbaceous and woody crops, winter plants during the winter. In addition to the direct effect of frost, plants are exposed to a number of other adverse factors. Temperatures can fluctuate significantly during winter. Frosts are often replaced by short-term and long-term thaws. In winter, snow storms are not uncommon, and in snowless winters in the more southern regions of the country, dry winds also occur. All this depletes the plants, which, after overwintering, come out very weakened and may subsequently die.

Especially numerous adverse effects are experienced by herbaceous perennial and annual plants. On the territory of Russia, in unfavorable years, the death of winter grain crops reaches 30-60%. Not only winter crops are dying, but also perennial grasses, fruit and berry plantations. In addition to low temperatures, winter plants are damaged and die from a number of other adverse factors in winter and early spring: wetting, wetting, ice crust, bulging, damage from winter drought.

Wetting, soaking, death under the ice crust, bulging, winter drought damage.

Damping out. Among the listed adversities, the first place is occupied by the decay of plants. The death of plants from damping off is observed mainly in warm winters with a large snow cover that lasts 2-3 months, especially if the snow falls on wet and thawed ground. Studies have shown that the cause of the death of winter crops from damping off is the depletion of plants. Being under snow at a temperature of about 0 ° C in a highly humid environment, almost complete darkness, i.e., under conditions in which the respiration process is quite intense and photosynthesis is excluded, plants gradually consume sugar and other nutrient reserves accumulated during the period passing through the first phase of hardening, and die from exhaustion (the content of sugars in tissues decreases from 20 to 2-4%) and spring frosts. Such plants are easily damaged by snow mold in spring, which also leads to their death.

Wetting. Wetting occurs mainly in spring in low places during the period of snow melting, less often during prolonged thaws, when melt water accumulates on the soil surface, which is not absorbed into the frozen soil and can flood plants. In this case, the cause of plant death is a sharp lack of oxygen (anaerobic conditions - hypoxia). In plants that are under a layer of water, normal respiration stops due to a lack of oxygen in water and soil. The absence of oxygen enhances the anaerobic respiration of plants, as a result of which toxic substances can be formed and plants die from exhaustion and direct poisoning of the body.

Death under the ice crust. Ice crust forms on fields in areas where frequent thaws are replaced by severe frosts. The effect of soaking in this case may be aggravated. In this case, the formation of hanging or ground (contact) ice crusts occurs. Hanging crusts are less dangerous, since they form on top of the soil and practically do not come into contact with plants; they are easy to destroy with a roller.

When a continuous ice contact crust is formed, the plants completely freeze into the ice, which leads to their death, since the plants, already weakened from soaking, are subjected to very strong mechanical pressure.

Bulging. Damage and death of plants from bulging are determined by ruptures in the root system. Bulging of plants is observed if frosts occur in autumn in the absence of snow cover or if there is little water in the surface layer of the soil (during autumn drought), as well as during thaws, if snow water has time to be absorbed into the soil. In these cases, the freezing of water does not begin from the surface of the soil, but at a certain depth (where there is moisture). The layer of ice formed at a depth gradually thickens due to the continued flow of water through the soil capillaries and raises (bulges out) the upper layers of the soil along with the plants, which leads to the breakage of the roots of plants that have penetrated to a considerable depth.

Winter drought damage. A stable snow cover protects winter cereals from drying out in winter. However, in conditions of a snowless or little snowy winter, like fruit trees and shrubs, in a number of regions of Russia they are often in danger of excessive drying out by constant and strong winds, especially at the end of winter with significant heating by the sun. The fact is that the water balance of plants develops extremely unfavorably in winter, since the flow of water from frozen soil practically stops.

To reduce the evaporation of water and the adverse effects of winter drought, fruit tree species form a thick layer of cork on the branches and shed their leaves for the winter.

Vernalization

Photoperiodic responses to seasonal changes in day length are important for the flowering frequency of many species in both temperate and tropical regions. However, it should be noted that among the species of temperate latitudes that exhibit photoperiodic responses, there are relatively few spring-flowering species, although we constantly encounter a significant number of "flowers blooming in spring", and many of these spring-flowering forms, for example, Ficariaverna, primrose (Primulavutgaris), violets (species of the genus Viola), etc., show pronounced seasonal behavior, remaining vegetative for the remainder of the year after abundant spring flowering. It can be assumed that spring flowering is a reaction to short days in winter, but for many species, this does not seem to be the case.

Of course, the length of the day is not the only external factor that changes throughout the year. It is clear that temperature also exhibits marked seasonal variations, especially in the temperate regions, although this factor exhibits considerable fluctuations, both daily and yearly. We know that seasonal changes in temperature, as well as changes in day length, have a significant impact on the flowering of many plant species.

Types of Plants Requiring Cooling to Proceed to Flowering.

It has been found that many species, including winter annuals, as well as biennial and perennial herbaceous plants, need to be chilled to transition to flowering.

Winter annuals and biennials are known to be monocarpic plants that require vernalization - they remain vegetative during the first growing season and bloom the following spring or early summer in response to the cooling period received in winter. The need for refrigeration of biennial plants to induce flowering has been experimentally demonstrated in a number of species such as beetroot (Betavulgaris), celery (Apiutngraveolens), cabbage and other cultivated varieties of the genus Brassica, bluebell (Campanulamedium), moongrass (Lunariabiennis), foxglove (Digitalispurpurea) and other. If digitalis plants, which under normal conditions behave like biennials, that is, bloom in the second year after germination, are kept in a greenhouse, they can remain vegetative for several years. In areas with mild winters, kale can grow outdoors for several years without the “arrowhead” (i.e., flowering) in spring, which usually occurs in areas with cold winters. Such species necessarily require vernalization, but in a number of other species flowering is accelerated when exposed to cold, but it can also occur without vernalization; such species showing facultative need for cold include lettuce (Lactucasaiiva), spinach (Spinacia oleracea) and late-flowering peas (Pistimsa-tivum).

As well as biennials, many perennials require cold exposure and will not flower without an annual winter chill. Of the common perennial plants, primrose (Primulavulgaris), violets (Violaspp.), lacfiol (Cheiranthuscheirii and C. allionii), levka (Mathiolaincarna), some varieties of chrysanthemums (Chrisanthemummorifolium), species of the genus Aster, Turkish carnation (Dianthus ), chaff (Loliumperenne). Perennial species require revernalization every winter.

It is likely that other spring-blooming perennials can be found to need refrigeration. Spring-flowering bulbous plants such as daffodils, hyacinths, blueberries (Endymionnonscriptus), crocuses, etc. do not require refrigeration to flower initiation because the flower primordia has been established in the bulb the previous summer, but their growth is highly dependent on temperature conditions . For example, in a tulip, the beginning of flowering is favored by relatively high temperatures (20°C), but for stem elongation and leaf growth, the optimal temperature at first is 8-9°C, with a gradual increase in later stages to 13, 17 and 23°C. Similar reactions to temperature are characteristic of hyacinths and daffodils.

In many species flower initiation does not take place during the cooling period itself, and begins only after the plant has been exposed to the higher temperatures following the cooling.

Thus, although the metabolism of most plants slows down considerably at low temperatures, there is no doubt that vernalization involves active physiological processes, the nature of which is as yet completely unknown.

Heat resistance of plants

Heat resistance (heat tolerance) - the ability of plants to endure the action of high temperatures, overheating. This is a genetically determined trait. Plant species differ in their tolerance to high temperatures.

According to heat resistance, three groups of plants are distinguished.

Heat-resistant - thermophilic blue-green algae and bacteria of hot mineral springs, capable of withstanding temperatures up to 75-100 °C. The heat resistance of thermophilic microorganisms is determined by a high level of metabolism, an increased content of RNA in cells, and resistance of the cytoplasmic protein to thermal coagulation.

Heat-tolerant - plants of deserts and dry habitats (succulents, some cacti, members of the Crassula family), withstanding heating by sunlight up to 50-65ºС. The heat resistance of succulents is largely determined by the increased viscosity of the cytoplasm and the content of bound water in the cells, and reduced metabolism.

Non-heat-resistant - mesophytic and aquatic plants. Mesophytes of open places tolerate short-term exposure to temperatures of 40-47 °C, shaded places - about 40-42 °C, aquatic plants withstand temperatures up to 38-42 °C. Of the agricultural crops, heat-loving plants of southern latitudes (sorghum, rice, cotton, castor beans, etc.) are the most heat-tolerant.

Many mesophytes tolerate high air temperatures and avoid overheating due to intensive transpiration, which reduces the temperature of the leaves. More heat-resistant mesophytes are distinguished by increased viscosity of the cytoplasm and increased synthesis of heat-resistant enzyme proteins.

Plants have developed a system of morphological and physiological adaptations that protect them from thermal damage: a light surface color that reflects insolation; folding and twisting of leaves; pubescence or scales that protect deeper tissues from overheating; thin layers of cork tissue that protect the phloem and cambium; greater thickness of the cuticular layer; high content of carbohydrates and low - water in the cytoplasm, etc.

Plants react very quickly to heat stress by inductive adaptation. They can prepare for exposure to high temperatures in a few hours. So, on hot days, the resistance of plants to high temperatures in the afternoon is higher than in the morning. Usually this resistance is temporary, it does not consolidate and disappears quite quickly if it gets cool. The reversibility of thermal exposure can range from several hours to 20 days. During the formation of generative organs, the heat resistance of annual and biennial plants decreases.

Drought tolerance of plants

Droughts have become a common occurrence for many regions of Russia and the CIS countries. Drought is a long rainless period, accompanied by a decrease in relative air humidity, soil moisture and an increase in temperature, when the normal water needs of plants are not met. On the territory of Russia there are regions of unstable moisture with an annual rainfall of 250-500 mm and arid regions with less than 250 mm of precipitation per year with an evaporation rate of more than 1000 mm.

Drought resistance - the ability of plants to endure long dry periods, significant water deficit, dehydration of cells, tissues and organs. At the same time, the damage to the crop depends on the duration of the drought and its intensity. Distinguish between soil drought and atmospheric drought.

Soil drought is caused by prolonged lack of rain combined with high air temperature and solar insolation, increased evaporation from the soil surface and transpiration, and strong winds. All this leads to desiccation of the root layer of the soil, a decrease in the supply of water available to plants at low air humidity. Atmospheric drought is characterized by high temperature and low relative humidity (10-20%). Severe atmospheric drought is caused by the movement of masses of dry and hot air - dry wind. Haze leads to serious consequences when a dry wind is accompanied by the appearance of soil particles in the air (dust storms).

Atmospheric drought, sharply increasing the evaporation of water from the soil surface and transpiration, contributes to the disruption of the coordination of the rates of water entering from the soil into the aboveground organs and its loss by the plant, as a result, the plant wilts. However, with a good development of the root system, atmospheric drought does not cause much harm to plants if the temperature does not exceed the limit tolerated by plants. Prolonged atmospheric drought in the absence of rain leads to soil drought, which is more dangerous for plants.

Drought resistance is due to the genetically determined adaptability of plants to habitat conditions, as well as adaptation to a lack of water. Drought resistance is expressed in the ability of plants to endure significant dehydration due to the development of high water potential of tissues with the functional preservation of cellular structures, as well as due to the adaptive morphological features of the stem, leaves, generative organs, which increase their endurance, tolerance to the effects of prolonged drought.

Plant types in relation to water regime

Plants of arid regions are called xerophytes (from the Greek xeros - dry). They are able in the process of individual development to adapt to atmospheric and soil drought. The characteristic features of xerophytes are the small size of their evaporating surface, as well as the small size of the above-ground part compared to the underground. Xerophytes are usually herbs or stunted shrubs. They are divided into several types. We present the classification of xerophytes according to P. A. Genkel.

Succulents are very resistant to overheating and resistant to dehydration; during a drought, they do not experience a lack of water, because they contain a large amount of it and consume it slowly. Their root system is branched in all directions in the upper layers of the soil, due to which the plants quickly absorb water during rainy periods. These are cacti, aloe, stonecrop, young.

Euxerophytes are heat-resistant plants that tolerate drought well. This group includes steppe plants such as Veronica gray, hairy aster, blue wormwood, watermelon colocynth, camel thorn, etc. They have low transpiration, high osmotic pressure, the cytoplasm is highly elastic and viscous, the root system is very branched, and its the mass is placed in the upper soil layer (50-60 cm). These xerophytes are capable of shedding leaves and even entire branches.

Hemixerophytes, or semi-xerophytes, are plants that are unable to tolerate dehydration and overheating. The viscosity and elasticity of their protoplast is insignificant, it is characterized by high transpiration, a deep root system that can reach subsoil water, which ensures an uninterrupted supply of water to the plant. This group includes sage, common cutter, etc.

Stipakserofshpy are feather grass, tyrsa and other narrow-leaved steppe grasses. They are resistant to overheating, make good use of the moisture of short-term rains. Withstand only short-term lack of water in the soil.

Poikiloxerophytes are plants that do not regulate their water regime. These are mainly lichens, which can dry out to an air-dry state and become active again after rains.

Hygrophytes (from the Greek hihros - wet). Plants belonging to this group do not have adaptations that limit water consumption. Hygrophytes are characterized by relatively large cell sizes, a thin-walled shell, weakly lignified walls of vessels, wood and bast fibers, a thin cuticle and slightly thickened outer walls of the epidermis, large stomata and a small number of them per unit surface, a large leaf blade, poorly developed mechanical tissues, a rare network of veins in the leaf, large cuticular transpiration, long stem, underdeveloped root system. By structure, hygrophytes approach shade-tolerant plants, but have a peculiar hygromorphic structure. A slight lack of water in the soil causes rapid wilting of hygrophytes. The osmotic pressure of cell sap in them is low. These include mannik, wild rosemary, cranberries, sucker.

According to the conditions of growth and structural features, plants with leaves partially or completely immersed in water or floating on its surface, which are called hydrophytes, are very close to hygrophytes.

Mesophytes (from the Greek mesos - medium, intermediate). Plants of this ecological group grow in conditions of sufficient moisture. The osmotic pressure of cell sap in mesophytes is 1-1.5 thousand kPa. They wilt easily. Mesophytes include most meadow grasses and legumes - creeping couch grass, meadow foxtail, meadow timothy, blue alfalfa, etc. From field crops, hard and soft wheat, corn, oats, peas, soybeans, sugar beet, hemp, almost all fruit (with the exception of almonds, grapes), many vegetable crops (carrots, tomatoes, etc.).

Transpiring organs - leaves are characterized by significant plasticity; depending on the growing conditions in their structure, quite large differences are observed. Even the leaves of the same plant with different water supply and lighting have differences in structure. Certain patterns have been established in the structure of leaves, depending on their location on the plant.

V. R. Zalensky discovered changes in the anatomical structure of leaves by tiers. He found that the leaves of the upper tier show regular changes in the direction of increasing xeromorphism, i.e., structures are formed that increase the drought resistance of these leaves. The leaves located in the upper part of the stem always differ from the lower ones, namely: the higher the leaf is located on the stem, the smaller the size of its cells, the greater the number of stomata and the smaller their size, the greater the number of hairs per unit surface, the denser the network of vascular bundles, the stronger palisade tissue is developed. All these signs characterize xerophilia, i.e., the formation of structures that contribute to an increase in drought resistance.

Physiological features are also associated with a certain anatomical structure, namely: the upper leaves are distinguished by a higher assimilation ability and more intensive transpiration. The concentration of juice in the upper leaves is also higher, and therefore water can be drawn by the upper leaves from the lower ones, the lower leaves may dry out and die. The structure of organs and tissues that increases the drought resistance of plants is called xeromorphism. Distinctive features in the structure of the leaves of the upper tier are explained by the fact that they develop in conditions of somewhat difficult water supply.

A complex system of anatomical and physiological adaptations has been formed to equalize the balance between the inflow and outflow of water in a plant. Such adaptations are observed in xerophytes, hygrophytes, mesophytes.

The results of the research showed that the adaptive properties of drought-resistant plant forms arise under the influence of the conditions of their existence.

CONCLUSION

The amazing harmony of living nature, its perfection are created by nature itself: the struggle for survival. Forms of adaptations in plants and animals are infinitely diverse. The entire animal and plant world, from the time of its appearance, has been improving along the path of expedient adaptations to living conditions: to water, to air, sunlight, gravity, etc.

LITERATURE

1. Volodko I.K. ""Microelements and resistance of plants to adverse conditions"", Minsk, Science and technology, 1983.

2. Goryshina T.K. ""Ecology of plants"", uch. Manual for universities, Moscow, V. school, 1979.

3. Prokofiev A.A. "Problems of drought resistance of plants", Moscow, Nauka, 1978.

4. Sergeeva K.A. "" Physiological and biochemical bases of winter hardiness of woody plants "", Moscow, Nauka, 1971

5. Kultiasov I.M. Ecology of plants. - M.: Publishing House of Moscow University, 1982