After being ground with liquid nitrogen, 0.1 g of callus material was homogenized in 2 mL of ice cold 50 mM K-phosphate buffer (pH 7.0) which contained 2 mM NaeEDTA and 1% (w/v) polyvinylpolypyrrolidone (PVP). The homogenate was centrifuged at
12,000 rpm min1 and 4 C for 10 min. After that, tissue extractwas stored at 80 C for subsequent analyses of SOD and CAT. The soluble protein content