Effect of Acclimation to High Temperatures on the Mechanisms of Drought Tolerance in Species with Different Types of Photosynthesis: Sedobassia sedoides (C3-C4) and Bassia prostrata (C4-NADP)

The effect of drought on the morphophysiological, biochemical, and molecular genetic parameters of plants Sedobassia sedoides (Pall.) Freitag & G. Kadereit with an intermediate C-3-C-4-type of photosynthesis and Bassia prostrata (L.) A.J. Scott with a C-4-NADP type of photosynthesis grown at different temperatures (25 and 30 & DEG;C) was studied. A decrease in the biomass, water content, and effective quantum yield (& phi;(PSII)) of PSII, as well as an increase in the expression of the psbA gene encoding the PSII D1 protein under the action of drought, was observed in both species regardless of the growing temperature. Both species showed a decrease in the content of photosynthetic enzymes ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and phosphoenolpyruvate carboxylase (PEPC) under drought conditions at 25 & DEG;C, which was accompanied by a significant increase in the expression of the rbcL and PPDK genes in S. sedoides. Acclimation of S. sedoides plants to elevated temperatures led to an increase in the activity of cyclic electron transport around PSI, to mitigation of the negative effect of drought on the light reactions of photosynthesis (reduction in NPQ) and the content of the PEPC enzyme, as well as to a shift in the ionic balance caused by a decrease in the potassium content. B. prostrata showed greater drought resistance and was characterized by greater thermolability of photosynthetic enzymes, changes in the content and ratio of which allowed this species to maintain growth in drought conditions at different temperatures.