The diseases of the spine - a large group of diseases that suffer over 85% ...
The temperature is the most important factor determining the possibilities and timing of the cultivation of crops.
The biological and chemical processes of transformation of nutrition elements are directly dependent on the temperature. The heat supply of crops is characterized by the sum of the average daily air temperature above 10 ° C for the growing season. Both high and low temperatures disrupt the flow of biochemical processes in cells, and thus can call in them the irreversible changes leading to the cessation of the growth and death of plants. The temperature rise to 25-28 ° C increases the activity of photosynthesis, and with further its growth begins to noticeably prevail breathing over the photosynthesis, which leads to a decrease in the mass of plants. Therefore, most agricultural crops at temperatures above 30 ° C, the waste carbohydrates for breathing do not give, as a rule, harvesting. Reducing the ambient temperature from 25 to 10 ° C reduces the intensity of photosynthesis and plants growth of 4-5 times. The temperature at which the formation of photosynthesis products is equal to their respiration consumption is called a compensation point.
The highest intensity of photosynthesis in plants of moderate climate is observed in the range of 24-26 ° C. For most field crops, the optimal temperature is 25 ° C, at night - 16-18 ° C. When the temperature increases to 35-40 ° C, photosynthesis is terminated as a result of violation of biochemical processes and excessive transpiration (Kuznetsov, Dmitriev, 2006). A significant deviation of the temperature from optimal in the direction of increasing or decrease significantly reduces the enzymatic activity in plant cells, the intensity of photosynthesis and the flow of nutrition elements in the plants.
The temperature has a great effect on the growth of the roots. Low (< 5°С) и высокие (> 30 ° C) Soil temperatures contribute to surface root location, significantly reduces their growth and activity. In most plants, the most powerful branched root system is formed at a temperature of the soil 20-25 ° C.
When determining the deadline for making fertilizers, it is important to take into account the significant effect of the soil temperature on the flow of nutrition elements in the plant. It has been established that at a temperature below 12 ° C, the use of phosphorus, potassium and trace elements from soil and fertilizers is significantly deteriorated, and the consumption of mineral nitrogen is also significantly reduced at temperatures below 8 ° C. For most crops, the temperature of 5-6 ° C is critical for the receipt of the main batteries in the plant.
The heat propulsion of the growing season is largely due to the structure of the sowing areas and the possibility of growing more productive late cultures, which for a long time can use solar energy on the formation of a crop or conduct repeated crops after the selected crops.
In the conditions of the non-sinnamine zone of Russia, there is a direct dependence of the productivity of crops on the amount of temperatures. In the forest-steppe and steppe zones, in irrigated conditions for any reliable communication between the number of positive temperatures and crops, farming crops are not established. In the central and southern regions of the country, the increase or decrease in the temperature by 2-3 ° C does not have a significant effect on plant productivity.
A great influence also has the temperature for the livelihood of soil microflora, which causes the mineral nutrition of plants. It has been established that the greatest intensity of ammonification of organic residues in the soil under the action of microorganisms occurs at a temperature of 26-30 ° C and soil moisture 70-80% of HV. The deviation of the temperature or humidity from optimal values \u200b\u200bsignificantly reduces the intensity of microbiological processes in the soil.
A large influence on the intensity of photosynthesis and fertilizer efficiency has a moisture supply of plants. The degree of disclosure of the mouth depends on the tour state of the plant, the rate of receipt in the leaves CO 2 and the allocation of 2. In the conditions of drought and excessive moisture of the ustitz usually closed and assimilation of carbon dioxide (photosynthesis) stops. The highest intensity of photosynthesis is observed with a small shortage of water in the sheet (10-15% of full saturation), when the ustitis is maximally disclosed. Only under the conditions of the optimal water regime, the root system of plants exhibits the highest activity of the consumption of nutritional elements from the soil solution. The moisture deficit in the soil leads to a decrease in the velocity of the movement of water and nutritional elements by xylene to the leaves, the intensity of photosynthesis and a decrease in the biomass of plants.
Not only the amount of precipitation is important, but also the dynamics of their distribution during the growing season in relation to individual cultures. The productivity of crops is largely due to the security of moisture in the most responsible phases of the growth and development of plants.
A dark correlation relationship between the yield and the amount of precipitation at the end of May - August for potatoes, corn, cornoplodes and vegetable crops has been established for the non-black-nosed zone. The lack of moisture in these periods significantly reduces the crop of plants and fertilizer efficiency.
The use of nitrogen and phosphoric-potash fertilizers significantly increases moisture deficit, since water consumption increases in proportion to the increase in the above-ground mass. It has been established that on the fertilized fields, the drying effect of plants on the soil begins to manifest itself earlier and at a greater depth than not fertilized. Therefore, with a deficiency of moisture, the fertilized fields are seeded, as early as possible, to the time of the occurrence of drought and drying the upper layer of the soil roots reached the lower more moisturized horizons. The most important event of moisture in steppe areas is snowstore, early harrowing for the closure of moisture and early sowing.
In the forest-steppe and dry-thermal zone, moisture supply is one of the most important factors of the productivity of crops.
In the zones of sufficient and excessive moistening, the washing water regime has a big effect on the provision of plant elements, since a significant amount of nitrogen, calcium, magnesium and soluble nitrogen, calcium, magnesium and soluble humus substances are made with a descending current of water from the roof. Such a mode is created, as a rule, in the fall and early spring.
A large influence on the yield of crops, fertilizer efficiency, strings and agrotechnical techniques of field work has exposure and relief of fields, since the slopes of different exposures and steepness are significantly different in humus content, power elements, thermal and water regimes and responsiveness of agricultural plants for fertilizers. The soils of the northern and northeastern slopes are usually more humus, better provided by moisture, above the snow cover, are later thawed compared to southern slopes and, as a rule, more severe particle size distribution. The soils of the southern and south-western slopes are warmer than the northern, they used to be thawed, characterized by intense flood drain and stormwater, from here, as a rule, more eroded, contain less or strong particles. In the soils of the southern slopes, the mineralization of short-root residues and organic fertilizers proceeds more intensively, so they are less humus. The higher the snow cover, the less the depth of the soil freezing, it absorbs the spring melting water better and the floods are less destroyed by the soil.
The characteristic of soils of different exposure is important to take into account when planning the timing of field work and the need for appliances to carry fertilizers, since after completion of field work on the southern slopes, it is used in the fields of the northern exposure.
Despite the greater dependence of the growth and development of plants from their provision of moisture and heat, which determines the role in the formation of crops crops in the non-black-earth zone and many other regions belongs to the fertility of the soil and applying fertilizers.
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For most plants, temperatures + 15 ... + 30 o C are most favorable for life at a temperature of + 35 ... + 40 o with most plants are damaged.
The action of high temperatures entails a number of hazards for plants: strong dehydration and drying, burns, chlorophyll destruction, irreversible respiratory disorders and other physiological processes, cessation of protein synthesis and enhancing their decay, accumulation of poisonous substances, in particular ammonia. At very high temperatures, the permeability of membranes is sharply increasing, and then thermal denaturation of proteins, coagulation of cytoplasm and cells of cells occurs. Overheating of the soil leads to damage and dying the surfaces of the roots, to the root cervous burns.
Primary changes in cellular structures occur at the level of membranes as a result of activating the formation of oxygen radicals and the subsequent peroxidation oxidation of lipids, disorders of the antioxidant system - the activity of superoxiddismutase, glutathionesondase and other enzymes. This causes the destruction of protein-lipid plasma complex complexes and other cell membranes, leads to the loss of osmotic properties of the cell. As a result, the disorganization of many cell functions is observed, reducing the speed of various physiological processes. Thus, at a temperature of 20 o, with all cells, the mitotic division is undergoed, at 38 o with mitosis, it is noted in each seventh cell, and the temperature increase to 42 ° C reduces the number of dividing cells 500 times.
At maximum temperatures, the consumption of organic substances for breathing exceeds its synthesis, the plant is poor in carbohydrates, and then begins to starve. This is especially sharply pronounced in plants of a more moderate climate (wheat, potatoes, many garden crops). With a general weakening, their susceptibility to fungal and viral infections increases.
Even a short-term stressing effect of high temperature causes the rearrangement of the hormonal plant system. Using the example of wheat and pea seedlings, it has been established that a thermal shock induces a whole cascade of multi-stage changes in the hormonal system, which is launched by the emission of the cowle from the pool of its conjugates performing the role of a stress signal and initiating ethylene synthesis. The result of ethylene synthesis is the subsequent reduction in the level of the IUC and an increase in the ABC. These hormonal restructuring obviously induce the synthesis of antioxidant protection and heat shock enzymes, cause a decrease in growth rates and as a result - the stability of the plant to the action of high temperatures increases.
There is a certain relationship between the conditions for the habitat of plants and heat-resistance. The land of habitat, the higher the temperature maximum, the more heat resistance of the plants.
The exposure to high temperatures plants can be prepared in a few hours. So, on hot days, the stability of plants to high temperatures after noon is higher than in the morning. Usually this stability is temporary, it is not fixed and quickly disappears, if it becomes cool. The reversibility of thermal exposure can be from several hours to 20 days.
Turnstanding is also connected with the plant development stage: young, actively growing fabrics are less stable than old. High temperatures are especially dangerous during flowering. Almost all generative cells in these conditions undergo structural changes, lose activity and the ability to divide, the deformation of pollen grains is observed, the weak development of the germinal bag and the appearance of sterile flowers.
They differ in heat-resistant and plant organs. The dehydrated organs are better tolerated: seeds up to 120 o C, pollen to 70 o C, disputes for several minutes withstand heating to 180 o C.
Of the fabrics are the most stable Cambial. So, the cambial layer in the trunks tolerates the temperature in the summer to +51 o C.
Effect of air temperature
The processes of vital activity in each type of plants are carried out at a certain heat mode, which depends on the quality of heat and the duration of its impact.
Different plants need a different amount of heat and have different ability to carry deviations (both in the direction of decrease and increase) temperature from optimal.
The optimal temperature is the most favorable temperature for a certain type of plant at a certain stage of development.
Maximum and minimum temperatures that do not disturb the normal development of plants, determine the limits of temperatures allowed for their cultivation in appropriate conditions. The decrease in temperature leads to a slowdown in all processes, is accompanied by the weakening of photosynthesis, the braking of the formation of organic substances, respiration, transpiration. Increase in temperature activates these processes.
It is noted that the intensity of photosynthesis is growing with an increase in temperature and reaches a maximum in the region of 15-20 for plants of moderate latitudes and 25-30 for tropical and subtropical plants. The daily temperature in the autumn in the interiors almost does not fall below 13. In winter, it is within 15-21. In the spring fluctuations in temperatures increase. It reaches 18-25. In the summer, the temperature remains relatively high during the day and is 22-28. As can be seen, the air temperature in the rooms is almost laid in the temperature range required for the flow of photosynthesis throughout the year. The temperature is thus not such a limiting factor in room conditions as the lighting intensity.
In winter, indoor pets feel fine at lower temperatures, because Many of them are at rest, and other growth processes slow down either temporarily stop. Therefore, heat needy decreases compared to summer.
The effect of light on the growth of plants - photomorphogenesis. The effect of red and far red light on the growth of plants
Photomorphogenesis - These are the processes occurring in the plant under the influence of light of various spectral composition and intensity. In them the light is not as the primary source of energy, but as signal means, adjusting Processes of growth and development of the plant. You can spend some analogy with street traffic lightautomatically regulating road traffic. Only for the management of nature chose not "red - yellow-deplex", and another set of colors: "Blue - red - long red".
And the first manifestation of photomorphogenesis occurs at the time of seed germination.
About the structure of the seed and the peculiarities of germination, I already talked in the article about seedlings . But there were omitted for details related to signal The action of light. Execute this gap.
So, the seed woke up from hibernation and began to germinate, while under the layer of the soil, i.e, darkness. I note at once that small seeds sown superficially and not sprinkled, they also germinate in darkness at night.
By the way, according to my observations, in general, all Raasada, standing in a bright place, germinates at night And you can see mass shoots in the morning.
But back to our unfortunate seed crumpled. The problem lies in the fact that even appearing on the surface of the soil, the sprout does not know about it and continues to actively grow, reach to the light, to life until he receives a special signal: stop, you can continue to be in a hurry, you are already free and you will live. (It seems to me that people did not have a red stop signal for drivers themselves, but stole him from nature ... :-).
And such a synal he does not receive from air, not from moisture, not from mechanical exposure, but from short-term light radiation containing red Part of the spectrum.
And before receiving such a signal, the seedlings are in the so-called higholic condition. In which it has a pale appearance and hooked baked shape. The hook is the outward outward epicotyl or hypocotyl, which is necessary to protect the kidnings (points of growth) in extinguishing through thorns to the stars, and it will continue if the growth continues in the dark and the plant will remain in this oriental state.
Germination
Light plays an extremely important role in the development of plants. Changes in the morphology of the plant under the influence of light radiation is called photomorphogenesis. After the seed germination through the soil, the first rays of the sun cause radical changes from a new plant.
It is known that under the influence of the red light, the seed germination process is activated, and under the influence of long-range red light is suppressed. Blue light also suppresses germination. Such a reaction is characteristic of species with small seeds, since small seeds have no sufficient supply of nutrients to ensure growth in the dark when the thickness of the Earth is passing. Small seeds germinate only under the influence of red light, beaten by a thin layer of land, while just short-term irradiation - 5-10 minutes a day. An increase in the thickness of the soil layer leads to the enrichment of the spectrum by far red light, which suppresses the germination of the seed. In species of plants with large seeds containing sufficient supply of nutrients, no light is required for induction of germination.
Normally from the seed first grows the root, and then escape appears. After that, as the sprout increases (as a rule, under the influence of light), secondary roots and shoots develop. Such coordinated progress is an early manifestation of the phenomenon of interrelated growth, when the development of the root system affects the growth of escape and vice versa. More than these processes are controlled by hormones.
In the absence of light, the sprout remains in the so-called oriental state, while it has a pale appearance and hooked shape. The hook is the outward epicotyl or hypocotyl needed to protect the growth point during germination through the soil, and it will continue if the growth continues in the dark.
Red light
Why this happens - a little more theory. It turns out that in addition to chlorophyll, in any plant there is another wonderful pigment called - phytochrome. (Pigment is a protein having selective sensitivity to a specific section of the spectrum of white light).
Feature phytochrome is that he can take two forms with different properties under the influence red Lights (660 nm) and far Red light (730 nm), i.e. He has the ability to photovascular. Moreover, alternate short-term lighting of topics or another red light is similar to manipulating with any switch that has the "On-OFF" position, i.e. Always retains the result of the last impact.
This property of phytochrome provides tracking over the time of the day (morning-evening), managing periodicity Vital activity of the plant. Moreover, lightnessor shadisiness One or another plant also depends on the characteristics of the phytochromes available in it. And finally, most importantly - blossom Plants also controls ... phytochrome! But about it - next time.
In the meantime, let's go back to our seedlings (well, why doesn't he be lucky ...) Phytochrome, unlike chlorophyll, is not only in the leaves, but also in semen. Participation of phytochrome in the process of germination of seeds for some plants such: just red shine stimulates Seed germination processes, and far red - presentseaman germination. (It is possible that that is why the seeds and germinate at night). Although it is not a regularity for all Plants. But in any case, the red spectr is more useful (it stimulates) than far red, which suppresses the activity of life processes.
But suppose that our seed is lucky and it sprouted, appearing on the surface in a conductive form. Now enough short-term lighting seedlings to start the process deethion: The growth rate of the stem is declining, the hook is straightened, the synthesis of chlorophyll begins, the semiodoli begin to be green.
And all this, thanks red Light. In the sunny daylight of ordinary red rays, more than long-range red, therefore the occasion of the plant is high, and at night it goes into an inactive form.
How to distinguish between these two close spectrum sites for the source of artificial lighting? If you remember that the red plot is bordered by infrared, i.e. thermal radiation, it can be assumed that the warmer "to the touch" radiation, the greater the infrared rays, and therefore far red Sveta. Put your hand under the ordinary incandescent light bulb or under the fluorescent lamp of daylight - and feel the difference.
Determination of farmland plants
The concept of low-temperature stress (COLD SHOOK) includes the entire set of recovery reactions of plants on the action of cold or frost, with reactions corresponding to the genotype of plants and manifest themselves at different levels of the organization of the plant organism from molecular to organisen.
Cold resistance - the ability of thermal-loving plants to carry the effect of low positive temperatures. Cold-resistant plants that are not damaged and do not reduce their productivity at a temperature of from 0 to + 10 ° C.
For most farm crops, low positive temperatures are almost harmless. Separate organs of thermal-loving plants have different stability to cold. In corn and buckwheat, the stems die faster, the rice is less resistant to leaves, and soybeans first damage the stiffs, and then leaf plates, the peanuts are most sensitive to cold the root system.
When exposed to cold, the loss of the turgore is the leaves due to the violation of the delivery of water to the transporting authorities, which leads to a decrease in the content of intracellular water. Hydrolytic processes are enhanced, non-gas nitrogen (proline and other nitrogen compounds), monosahara accumulate. The heterogeneity and the amount of protein, especially low molecular weight (26, 32 kD) increase.
The permeability of membranes increases. This reaction relates to the primary mechanisms for the influence of cold. The change in the state of the membranes at low temperature is largely due to the loss of calcium ions. In winter wheat, if the impact is not too strong, the cell membranes lose calcium ions, the permeability increases; Various ions, primarily potassium, as well as organic acids and sugars from the cytoplasm goes into the cell wall or interclausers. Calcium ions also go into the cell wall, but their concentration and in cytoplasm increase, with H + -TF-AZA is activated. The active transport of protons launches secondary active transport, and potassium ions are returned to the cage. As a result, the absorption of water and those substances that came out of the cell, i.e. Cellular juice from the extractal space enters it, which leads to the restoration of its state after damage (Fig. 24a).
Under the action of a lower temperature, the loss of calcium ion membranes is very large. As a result of a strong exposure, the number of calcium ions in the cytoplasm increases, and membrane structures are violated, as well as the functions of membrane-bound enzymes. H + -atf-Aza is inactivated, and phospholipids, on the contrary, are activated, which causes the leakage of ions and stimulates the degradation of membrane lipids. In this case, damage becomes irreversible.
The change in the permeability of the membrane is also associated with shifts in fatty acid components: saturated fatty acids from the liquid crystal state are moving to the state of the gel earlier than unsaturated. Therefore, the larger in the membrane of saturated fatty acids, the more tougher, i.e. Less labil. With an increase in the level of unsaturated fatty acids, it was possible to reduce the sensitivity to a decrease in temperature.
Disintegration of membranes contributes to an increase in the content of free radicals, indicating the strengthening of lipid peroxidation (floor). For example, rice at 2 ° C reduced activity in the tissues of the antioxidant enzyme soda and the content of Malon Dialdehyde (MDA) - the final product of the floor increased. When processing with tocopherol, the number of MDA decreased.
The disorder of the integrity of the membrane leads to the decay of cellular structures: mitochondria and chloroplasts swell, the number of crystas and thylacoids decreases, vacuoles appear, the EPR form concentric circles, including from the tonoplast inside the vacuole. These are nonspecific changes.
Due to the disintegration of thylacoid membranes of chloroplasts, photosynthesis is disturbed, as for the ETC, and the Calvin cycle enzymes.
Damage to the respiratory process is also observed in cold weather, the decrease in energy efficiency is associated with additional costs of maintaining metabolism. The activity of an alternative way of breathing increases. In some cases, for example, Aroid, the intensification of this path contributes to the temperature of the colors in cold weather, which is necessary for evaporating essential oils that attract insects. The ratio of breathing paths in favor of the pentosophosphate path is changed.
In thermal-loving plants, complete inhibition of photosynthesis occurs at 0 ° C, because There is a violation of the membranes of chloroplasts and the disagreement of the transport of electrons and photosynthetic phosphorylation. In non-fat-resistant varieties of corn in 20 hours after the temperature of + 30s, the decay of chloroplasts and the destruction of pigments occurs. In cold-resistant hybrids, such as corn, the effect of temperature + 3 ° C does not affect the composition of the pigments and the structure of chloroplasts.
The effect of temperature on photosynthesis depends on the illumination. The formation of chlorophyll in the leaves of cucumber with a tempering temperature (+ 15 ° C) is inhibited less at a weaker illumination. The growth is inhibited, the balance of phytogormons changes - the ABC content increases (mainly in sustainable varieties and species), and the auxine is there. A decrease in temperature leads to changes in the transport processes: the absorption of NO3 is weakening, and NH4 is enhanced, especially in adapted plants. The most vulnerable under the action of low temperatures is transporting NO3 from the roots in the leaves.
The prolonged action of low temperatures leads a plant to death. The main reasons for the fusion of plants consist in an irreversible increase in the permeability of membranes, damage to the cell metabolism, the accumulation of toxic substances.
The negative impact of the cold depends on the temperature range and the duration of their impact. Already non-extremal low temperatures adversely affect plants, because:
- basin the main physiological processes (photosynthesis, transpiration, water exchange, etc.),
- reduce energy efficiency of breathing,
- change the functional activity of membranes,
- they lead to a predominance in the exchange of substances of hydrolytic reactions.
Externally damage to the cold is accompanied by the loss of the leaf of the turgora and the change in their color due to the destruction of chlorophyll. The main reason damaging action low positive temperatures The heat-loving plants - a violation of the functional activity of membranes due to the transition of saturated fatty acids from the liquid crystal state in the gel. As a result, on the one hand, the permeability of membranes for ions increases, and on the other, the activation energy of enzymes associated with the membrane increases. The rate of reactions catalyzed by membrane enzymes is reduced after the phase transition faster than the rate of reactions associated with soluble enzymes. All this leads to unfavorable shifts in metabolism, sharp increase in the number of endogenous toxicants, and with a long-term action of a low temperature to the death of the plant.
It has been established that action low negative temperatures It is depending on the state of plants and, in particular, from the hydrofit of the body tissues. Thus, dry seeds can decrease the temperature to -196 ° C (temperature of liquid nitrogen). This shows that the destructive effect of low temperature is fundamentally different from the effect of high temperature, causing direct coagulation of proteins.
Basic damaging effect Ice formation has ice formation. With the ice can form as in the cell itself and out of the cell. With a rapid decrease in temperature, ice formation occurs inside the cell (in cytoplasm, vacuoles). With a gradual decrease in the temperature of the ice crystals are formed primarily in interclausers. Plasmalemma prevents the penetration of ice crystals inside the cell. The content of the cell is in a supercourse state. As a result of the initial ice formation outside the cells, the aqueous potential in the intercellular space becomes more negative compared to the aquatic potential in the cell. There is a redistribution of water. The equilibrium between the content of water in interclauders and in the cell is achieved due to:
- either the outflow of water from the cell,
- either the formation of intracellular ice.
If the rate of outflow of water from the cell corresponds to the temperature of lowering the temperature, then the intracellular ice is not formed. However, the death of the cell and the body as a whole can occur as a result of the fact that the ice crystals formed in interclauders, pulling water from the cell, cause its dehydration and simultaneously have a mechanical pressure damaging cell structures on a cytoplasm. This causes a number of consequences:
- loss of Turgora
- increasing the concentration of cell juice,
- sharp decrease in cell volume,
- shift of pH values \u200b\u200bin an unfavorable side.
The stability of plants to low temperatures is divided into cold resistance and frost resistance.
Cool resistance of plants - The ability of thermal-loving plants to carry low positive temperatures. Protective value under the action of low positive temperatures on thermal loving plants has a number of devices. First of all, it is maintenance stability membranes and preventing ion leakage. Sustainable plants differ in greater fractions of unsaturated fatty acids in the composition of phospholipids membranes. This allows you to maintain the mobility of membranes and protects against destruction. In this regard, the enzymes of acetyltransferase and desaturases are a major role. The latter lead to the formation of double bonds in saturated fatty acids.
Adaptive reactions Low positive temperatures are manifested in the ability to maintain metabolism when it decreases. This is achieved by a wider temperature range of enzymes, synthesis of tread connections. In stable plants, the role of the pentosophosphate path of breathing increases, the efficiency of the antioxidant system, stress proteins are synthesized. It is shown that under the action of low positive temperatures, the synthesis of low molecular weight proteins is induced.
To increase the cold resistance, pre-sowing seed soaking is used. Effective is the use of trace elements (Zn, Mn, Cu, B, Mo). Thus, the soaking of seeds in solutions of boric acid, zinc sulfate or copper sulfate increases plant farmers.
Plant frost resistance - The ability of plants to carry negative temperatures.
Plant adaptation to negative temperatures. There are two types of adaptations to the action of negative temperatures:
- care from the damaging effect of factor (passive adaptation),
- improving survival (active adaptation).
Care from damaging low temperatures is achieved, first of all, due to short ontogenesis is care in time. For annual plants, the life cycle ends before the onset of negative temperatures. These plants before the onset of autumn cold weather have time to give seeds.
Most of the perennials loses their overhead organs and overwhelms in the form of bulbs, tubers or rhizomes, well-protected from frost with a layer of soil and snow - this care in space From the damaging action of low temperatures.
Hardening - This is a reversible physiological adaptation to adverse effects, which is happening under the influence of certain external conditions, refers to active adaptation. The physiological nature of the process of hardening to negative temperatures was disclosed thanks to the works of I.I. Tumanova and his schools.
As a result of the process of hardening, the frost resistance of the body sharply rises. Not all vegetable organisms have the ability to hardenize, it depends on the type of plant, its origin. Plants of southern origin to hardening are not capable. In plants of northern latitudes, the process of hardening is dedicated only to certain stages of development.
Plant hardening takes place in two phases:
First phase Hardening passes on light with several reduced positive temperatures (during the day about 10 ° C, at night about 2 ° C) and moderate humidity. A further slowdown continues in this phase, and even a complete stop of growth processes.
Of particular importance in the development of plant resistance to the frost in this phase, the accumulation of substances-cryoprotectors performing the protective function: sucrose, monosaccharides, soluble proteins, etc. accumulating in cells, sugars increase the concentration of cell juice, reduce the aqueous potential. The higher the concentration of the solution, the lower its freezing point, therefore the accumulation of sugars stabilizes cellular structures, in particular chloroplasts, so that they continue to function.
Second phase Hardening occurs with the further decrease in temperature (about 0 ° C) and does not require light. In this regard, for herbaceous plants, it can flow under the snow. This phase occurs outflow of water from cells, as well as the restructuring of the protoplast structure. The neoplasm of specific proteins resistant to dehydrate proteins continues. The change in the intermolecular bonds of cytoplasm proteins is important. With dehydration occurring under the influence of gland formation, there is a convergence of protein molecules. The links between them are rushing and are not restored in the same due to the too strong rapprochement and deformation of protein molecules. In this connection, the presence of sulfhydryl and other hydrophilic groups, which contribute to the holding of water and prevent the approach of the protein molecules. The restructuring of cytoplasm contributes to an increase in its permeability for water. Due to the more rapid outflow of water, the danger of intracellular ice formation decreases.
