Two grams of seeds were ground in a mortar and
homogenized in 20 ml of 0.1 M phosphate buffer (pH 7.8)
containing 0.4 g polyvinyl pyrrolidone, 2 mM dithiothreitol
and 0.1 mM EDTA followed by centrifuging at 16,000 g for
15 min at 4 8C. Catalase (CAT) activity was measured by
adopting the method of Clairborne (1985) and the concentration
of H2O2 was calculated using the extinction coefficient
0.036 mmol1 ml1. Superoxide dismutase (SOD), peroxidase
(POX) and ascorbic acid oxidase activity was measured
following Beauchamp and Fridovich (1971) and Sadasivamand
Manickam (1986), respectively, and the variation in enzyme
activity was deduced as per absorbance.