Diversity of Photosynthetic Activity of Organs of Wheat Genotypes: Breeding of High Yielding Varieties Tolerant to Water Stress.

Abstract

Under the water stress condition, active photosynthetic function of different assimilating organs and mainly of an ear, together with an optimal architectonics of plants play a decisive role in yield formation. In drought tolerant intensive varieties more than 60% of grain formation and protein synthesis occurs by an account of ear photosynthesis. Depending on a value of ear photosynthesis and tolerance of plants under strong drought conditions, the genotypes accumulate 35-70% of proteins from their contents in plants under the normal water supply. C4-cycle enzymes (PEP-carboxylase, NAD- and NADP-malate dehydrogenase) in C3-plants play a certain role in their adaptation to stress. High-yielding wheat genotypes tolerant to water stress have high activity of C4-cycle enzymes in the leaves and elements of ear; under the water stress the C4-cycle enzymes are activated. High- productive genotypes differ by the high intensity of CO2 assimilation and by the rate of photorespiration. The value of ratio of true photosynthesis to photorespiration in the leaves and in ear elements in genotypes with various rate of CO2 assimilation are close and equal at an average to 3:1 with increase of the given ratio in intensive genotypes. Thus, it is possible to denote the parallel increase of the intensity of true photosynthesis and photorespiration in ontogenesis of leaves and therefore the attempt to reduce photorespiration with the purpose of increase of the productivity is inconsistent. By increasing of a tolerance of genotypes to water stress or with increasing of drought the rate of photorespiration decreased in a large degree in the elements of ear. As a matter of investigation the series of genotypes with high activities of the primary processes and photosynthetic CO2 metabolism under water stress, having the appropriate morphophysiological characters were revealed. Using of these genotypes with main photosynthetic parameters connected with an intensity of ear activity and with activities of other non-leaf organs and high productivity of a grain protein is the base of creation of high tolerant varieties.