GENOTYPIC PECULIARITIES OF WHEAT PHOTOSYNTHESIS LIGHT INDUCTION AND PRODUCTIVITY UNDER THE DROUGHT EFFECT

Abstract

Background. In agrocenoses, leaf light conditions are known to be unstable due to intermittent cloud cover and shading by other leaves or spikes. However, with a change in irradiance, photosynthesis does not reach its final value instantly, but with a certain delay. Due to this photosynthetic efficiency of leaves and crops is generally lower compared to stationary conditions. At the same time, the vast majority of works devoted to the problems of photosynthetic apparatus functioning under unstable light conditions do not take into account an adverse impact on photosynthesis of such a common stressor as drought. The aim of the present work was to study the peculiarities of flag leaves CO₂ and H₂O gas exchange parameters with changes in illumination under conditions of optimal and insufficient water supply in order to explore the pattern of drought effect on the photosynthetic induction processes in connection with productivity of wheat plants of different genotypes.
Materials and Methods. The research was carried out on bread winter wheat varieties Yednist, Bohdana, Perlyna Podillia under conditions of pot experiment. Control plants were grown under an optimal soil moisture of 70 % field capacity (FC). In the experimental pots, soil drought was created at the level of 30 % FC for 7 days during the earing–flowering period, after that the soil moisture was restored to the optimal level. The parameters of flag leaf gas exchange were measured on the seventh day of drought. Components of plants grain productivity were determined after reaching full grain maturity.
Results. It was found that according to the parameters of light induction curves of CO₂ assimilation and transpiration, wheat plants of different genotypes under drought conditions are differentiated more clearly than under normal water supply. An increase in the limiting role of stomata in the induction of photosynthesis under drought conditions and changes in illumination was shown. Drought disrupts the coherence of stomatal
conductance regulation in interaction with CO₂ assimilation processes. This affects the light induction curves of photosynthesis and transpiration, and ultimately leads to a decrease in grain productivity.
Conclusions. It was shown that in order to assess the efficiency of the photosynthetic apparatus in providing wheat plants with assimilates and maintaining their grain productivity under unfavorable conditions, the parameters of the response to the changes in illumination must be taken into account.