Effect of Exogenous Treatment with Salicylic Acid on Photosynthetic Activity and Antioxidant Capacity of Chilled Wheat Plants

The effects of salicylic acid (SA) and cold on photosynthesis, activities of carboxylating enzymes ribulose-1,5bisphosphate carboxylase (RuBPC) and phosphoenolpyruvate carboxylase (PEPC) and activities of photorespiratory enzymes glycolate oxidase (GO) and catalase (CAT), and on the activies of antioxidant enzymes superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR) and peroxidase (POX) were investigated in winter wheat (Triticum aestivum, cv. Dogu-88) leaves. Exposure of wheat plants to a low temperature (3 oC) for 48 h and 72 h resulted in decreased levels of chlorophyll, CO2 assimilation and transpiration rates and increased activity of GO and CAT. Treatment with SA alone for 24 h resulted in a lower rate of photosynthesis, decreased transpiration and stomatal conductance accompanied with enhanced rate of lipid peroxidation and peroxides level. Treatment with 500 μmol/L SA for 24 h before exposure to chilling provided protection on RuBPC activity and chlorophyll content. The activities of GO, CAT, POX, and APX additionally increased in SA-treated plants. The impact of SA and cold on photorespiratory and antioxidative