Effect of Elevated CO₂ Concentrations on Drought and Heat Tolerance of the C₄-NADP Species Kochia prostrata.

Rakhmankulova, Z. F.; Shuyskaya, E. V.; Prokofieva, M. Yu.; Kazantseva, V. V.; Saidova, L. T.; Zagoskina, N. V.; Voronin, P. Yu.

The effect of elevated CO2 (eCO2) on changes in the morphophysiological, biochemical, and molecular genetic parameters of the C4-NADP halophyte Kochia prostrata (L.) Schrad. under short-term water deficit (WD) and/or elevated temperatures (eT) was studied. The changes in the parameters of growth, water–salt balance, CO2/H2O gas exchange, PSII efficiency, PSI cyclic electron transport (CET) activity, photosynthetic gene expression, key carboxylation enzyme content, and antioxidative system activity were studied. Plants reacted more negatively to water deficit than to other individual factors (eCO2 or eT). The expression of genes encoding components of PSI (psaA, psaB), ribulose-1,5-bisphosphate carboxylase/oxygenase Rubisco (rbcL), and pyruvate phosphate dikinase (PPDK) was downregulated, and a decrease was observed in the content of the photosynthetic enzymes Rubisco and phosphoenolpyruvate carboxylase (PEPС) and fresh biomass, PSII efficiency, apparent photosynthesis, and transpiration rates, indicating a stomatal and metabolic limitation of photosynthesis associated with insufficient functioning of the C4 carbon-concentrating mechanism. eT did not significantly affect the growth parameters and water–salt balance of K. prostrata. Decreased apparent photosynthesis intensity at eT was mainly associated with stomatal limitation (decreased transpiration). The most severe stress was caused by eT WD. A decrease in psaA, psaB, rbcL, and PPDK expression, PSII efficiency and PSI CET activity, photosynthesis and transpiration intensity, fresh biomass and water content and an increase in proline accumulation and oxidative stress indices were observed. The effect of eCO2 mitigated the negative effect of individual and combined water deficit and temperature stress on CO2/H2O gas exchanges (apparent photosynthesis, transpiration) but enhanced their negative effect on PSII functioning. Additionally, under eT WD, eCO2 contributed to a significant increase in proline content and the activation of antioxidant defense, with the participation of catalase, phenolic compounds, and PSI CET. Overall, eCO2 affected the mechanisms of homeostatic water balance and antioxidant defense and the ratio of light and dark reactions of photosynthesis during the adaptation of K. prostrata to drought and/or eT compared with ambient CO2 conditions.

Russian Journal of Plant Physiology, 2024, Vol 71, Issue 3, p1

1021-4437

Academic Journal

10.1134/S1021443724605275