Determination of activities of antioxidant enzymes and hydrogen peroxide concentration
Leaf samples were homogenized in a pre-chilled mortar and pestle placed on ice with 3 mL potassium phosphate buffer . The homogenate was centrifuged at for 20 min at and the supernatant was used to determine enzymes activities. Superoxide dismutase activity was measured following the method described by Giannopotitis and Ries (Giannopolitis & Ries, 1977). The activity of peroxidase (POD) were analyzed through measuring the oxidation of guaiacol (Raoet al ., 1996). Catalase activity was assayed using the method by Aebi (Aebi, 1984). Hydrogen peroxide (H2O2) analyses were conducted as described previously (Alexieva et al ., 2001).