PARENT SESSION
Posters P3B Photosynthetic acclimation: Ecophysiology, diverse environments. Abstracts (479-522)

Effects of water stress on photochemistry and on the thermotolerance of Photosystem II in wheat plants. Mubariz Ismayilov^*,1, Jalal Aliyev¹, ¹ Institute of Botany of Azerbaijan National Academy of Sciences, Baku, Azerbaijan

ABSTRACT- Chlorophyll fluorescence and slow fluorescence kinetics were used to evaluate PS II photochemistry in wheat plants subjected to water stress. Water stress showed no effects on the maximal quantum yield of PS II photochemistry (F_V/F_M), slow fluorescence kinetics in dark-adapted wheat leaves, indicating that water stress had no effects on the primary photochemistry of PS II. A slight but significant decrease in the quantum yield of PS II electron transport (F/F_M) was observed in severely drought wheat plants. This suggested that decline in the rate of net CO₂ assimilation in wheat plants during drought progression was mostly due to stomatal closure, and that the photosynthetic apparatus of wheat was impaired by severe water stress. In addition, simultaneous treatment of drought and high temperatures protects the thermostability of PS II, which was reflected in a less decrease in F_V/F_M and F/F_M in water-stressed leaves than in well-watered leaves. It was suggested that increased thermostability of PS II may be associated with an improvement of resistance of reaction centers and O₂-evolving complex in water-stressed wheat plants to high temperatures.

KEY WORDS: photosystem II, wheat (Triticum durum L.), chlorophyll fluorescence, water stress