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Fitness of ontogenesis of plants to conditions of the environment is result of their evolutionary development (an, heredities, selection. Throughout a phylogeny of a species of plants in the course of evolution requirements of an individual to living conditions and fitness to the ecological niche occupied by it were developed. Vlagolyubiye and shade tolerance, heat tolerance, a and other ecological features of concrete species of plants were created during evolution as a result of action of the corresponding conditions. So, thermophilic plants and plants of short day are characteristic for southern latitudes, less exacting to heat and plants of long day — for northern.

The ice which is formed at slow frost penetration in mezhkletochnik and cellular walls delays water from cages; cellular juice becomes, changes Wednesdays. ­ ice works as dry air, drying up cages and strongly changing their osmotic properties. Besides, cytoplasm to compression by ice crystals. The formed crystals of ice force out air from mezhkletochnik therefore the frozen leaves become transparent.

In the nature in one geographical region each type of occupies the ecological niche corresponding to its features: the hygrophilous — are closer to reservoirs, shade-enduring — under wood bed curtains etc. Heredity of plants is formed under the influence of certain environmental conditions. Also external conditions of ontogenesis of plants are important.

Degree of cold constancy of different plants is not identical. Many plants of southern latitudes are damaged by cold. At a temperature of 3 °C the cucumber, a cotton, haricot, a, an eggplant are damaged. Cold resistance at grades is various. For the characteristic of cold constancy of plants use concept a temperature minimum at which growth of plants stops. For big group of agricultural plants its size makes 4 °C. However many plants have higher value of a temperature minimum and respectively they are less steady against influence of cold.

Damage of plants by cold is followed by loss of turgor by them and an of coloring (because of destruction a chlorophyll that is a consequence of violation of transport of water to transpiriruyushchy bodies. Besides, considerable violations of physiological functions which are connected with violation of an of nucleinic acids and proteins are observed. DNA chain-> RNA-> protein-> a sign is broken.