The is caused by genetically certain of plants to habitat conditions, and also an to a lack of water. Drought resistance is expressed to have considerable dehydration due to development of high water potential of fabrics at safety of cellular structures to of plants, and also due to morphological features of a stalk, leaves, bodies increasing their endurance, tolerance to action of a long drought.
Usually atmospheric and soil droughts accompany each other. Purely atmospheric drought quite often comes when the soil is still saturated water after a snow descent. The drought is often observed in the middle or the end of summer when winter reserves of moisture are already settled, and summer rainfall it appeared insufficiently. The soil drought always reduces a crop and if it begins very much early, can lead to full loss of a crop.
The soil drought is caused by the long absence of rains in combination with high temperature of air and a solar raised by evaporation from a surface of the soil and a trance-piratsiyey, strong winds. All this leads to a siccation of a korneobitayemy layer of earth, decrease in a reserve of water, available to plants, at the lowered humidity of air. The atmospheric drought is characterized by high temperature and low humidity of air (10 — 20%). The rigid atmospheric drought is caused by movement of mass of a dry and hot — a dry wind. The haze when the dry wind is followed by emergence in air of soil particles (dust storms) leads to serious consequences.
at delay with their crops. For example, wheat in a kusheniye phase in a cone of increase has a differentiation of cones. High temperature of the soil and air leads to damage of a cone of increase, accelerates process and reduces time of a of the IV—V stages, the number of cones in an ear, and also number of flowers in a cone that brings to a crop as a result decreases.
ny kserofit are curtailed and an ustyitsa appear in a tube. In such state these plants are capable to transfer long dehydration (the content of water can fall to 25%), falling into anabiosis. However at improvement a they quickly pass to normal activity. Except these three types of the real kserofit in deserts false kserofita — ephemeral plants — the plants avoiding a thanks to short life cycle (one and a half-two , dated for the period of rains. On all other properties ephemeral plants — typical mezofita. The considered types, of course, do not cover all variety of transitional forms.
For mezofit and kserofit in the conditions of deficiency of water of a three main ways of protection: prevention of loss of water cages (drying avoiding); drying; avoiding of the period of a drought. Let's stop on the characteristic of different types of kserofit. The only thing the sign, general for all kserofit, are the insignificant sizes of the evaporating surface.
At action of high temperatures in cages of plants synthesis of stressful proteins (proteins thermal shock. Plants of dry, light habitats more a rack by a heat, than shade-loving. Short-term influence very high distemper -
On a method F. F. Matskova leaves of the studied plants lower consistently for 30 min. in the warmed-up water at temperatures of 40, 45, 5. to 80 °C, and then in cold water for 10 min., every time is selected by tests and after cold water transfer to 0,2 N. The nanoseconds which Died off (sites are damaged and dead leaves buret. Comparative heat tolerance of plants is determined also by change of permeability of a and other methods.