Oxidative metabolism in tomato plants subjected to heat stress

SummaryTomato plants (Lycopersicon esculentum L. cultivar Tmknvf2) were grown for 30 d at two temperatures (25°C, optimal temperature, and 35°C) with the objective of determining the effect of heat stress on oxidative metabolism. The leaf concentrations of the antioxidant compounds ascorbate (AsA), dehydroascorbate (DHA), reduced glutathione (GSH), oxidized glutathione (GSSG) and the activities of the enzymes superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (GPX), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR) and glutathione reductase (GR), as well as total hydrogen peroxide (H2O2) concentration and shoot dry weight, were determined. High temperature stress caused: (1) decreased shoot weight, (2) accumulation of H2O2, (3) increased SOD activity, (4) decreased activities of CAT, GPX, APX, DHAR, GR (associated with detoxifying H2O2), and (5) increased levels of the antioxidant compounds AsA, DHA, GSSG, and GSH. In addition, our data demonstrated that heat stress occurred in tomato plants at 35°C, and this temperature may have initially inhibited the ascorbate/glutathione cycle and then provoked an oxidative burst, indicated by foliar H2O2 accumulation.