PLANT RESPONSES TO A SHORT-TERM DAILY TEMPERATURE DROP: EFFECT OF PHOTOPERIOD AND COMPARISON OF PLANTS FROM DIFFERENT PHOTOPERIODIC GROUPS

In a controlled environment, the effect of zinc deficiency on the photosynthetic apparatus (PSA) of 7-day-old winter wheat seedlings ( Triticum aestivum L.) cv. Moskovskaya 39 was studied. It was shown that in the early phases of seedling development, the zinc lack in the root environment does not clearly affect the plant shoot height and accumulation of dry biomass, but it has a negative effect on a number of PSA parameters. In particular, the leaf area of the 1-st leaf decreased and the photosynthetic pigments (chlorophylls and carotenoids) content and stomatal conductance declined. At the same time, with the microelement deficient, a redistribution of chlorophylls towards the light-harvesting complexes (LHC) of photosystems was noted, aimed at increasing light absorption. No significant changes in the ratio of chlorophylls ( a / b ) and the photosystem II (PS II) activity which was determined by the F v /F m parameter, characterizes the potential quantum yield of photochemical activity of PS II, were found. In addition, the rate of photosynthesis was maintained at a high level in seedlings deficient in zinc, and the integrity of cell membranes was maintained, which largely ensured their normal growth and accumulation of dry biomass. It has been suggested that the negative effect of zinc deficiency on a number of PSA parameters in seedlings may subsequently be one of the reasons for the decrease in wheat seed productivity indicated in the literature under these conditions.