Distinguish two types of a zavyadaniye: temporary and deep. The atmospheric drought when in the presence of available water in the soil it does not happens of a temporary zavyadaniye of plants usually to come to a plant and to compensate its expense. At a temporary zavyadaniye turgor of leaves is restored in and night hours. The temporary zavyadaniye reduces a of plants as at loss of turgor of ustiyets are closed
Resistance to a drought is expressed that these plants are capable to regulate intensity of a transpiration at the expense of a of the ustyichny device, droppings leaves and even the zavyazy. For more drought-resistant types and grades are characteristic the developed root system, rather high root pressure, a the water-retaining ability of fabrics caused by accumulation in vacuoles of osmotically active agents (, organic acids, soluble forms of nitrogen and ions mineral.
The lack of water of fabrics of plants results from excess of its expense on a transpiration before receipt from the soil. It often in a hot sunny weather to the middle of day. Thus the content of water in leaves decreases by 25 — 28% in comparison with morning, plants lose turgor and fade. As a result also the water potential of leaves that makes active waters from the soil in a plant decreases.
At the accruing dehydration at not drought-resistant during the first period of a zavyadaniye intensity of breath perhaps because of a large number of simple products (hexoses) of hydrolysis of polysaccharides, generally starch, and then gradually decreases. However the energy which is distinguished in process a does not accumulate in ATP, and dissipates in the form of warmth (single breath. At action on plants of high temperature (45 °C) and a dry wind there are profound structural changes of mitochondrions, damage or inhibition of of the fosforiliruyushchy mechanism. All this testifies to violation of a power exchange of plants. In roots and a pasoka the content of amides raises. Growth of a plant, especially leaves and stalks is as a result slowed down, the crop decreases. At more drought-resistant plants all these changes less a.
From physiological processes by the most sensitive to a lack of moisture growth process which rates at the accruing lack of moisture decrease photosynthesis and breath much earlier is. Growth processes are late even after water supply restoration. At the progressing dehydration a certain sequence in operation of a drought on separate parts of a plant is observed.
Drought resistance of agricultural plants — is the complex sign connected with a number of their physiological features. Drought-resistant plants of a to have temporary dehydration with the smallest of growth processes and productivity. According to I. I. Tumanov, the long zavyadaniye caused by drying of the soil is reflected in a millet crop a little, but very strongly an oat crop. N. A. Maximov (195 notes that there is no type of drought resistance of crops as there are no universal signs of drought resistance also. From the general signs it should be noted smaller negative of dehydration and faster restoration of physiological functions after a drought at more types and grades of crops.
formation of CO2; violations of structure of hloroplast; delays of outflow of assimilyat from leaves. According to V. A. Brilliant (192, reduction of an ovodnennost of a leaf at sugar beet for 3 — 4% leads to decrease in photosynthesis by 76%.