sample were incubated at 25 C for 1 min, and the change in
absorbance at 398 nm with time was recorded. Catalase (CAT) and
Superoxide dismutase (SOD) were assayed following the methods
ofWang and Tian (2005). CAT was extracted by 50 mmol/L sodium
phosphate buffer (pH 7.0). The reaction mixture consisted of 2 mL
sodium phosphate buffer (50 mmol/L, pH 7.0), 0.5 mL H2O2
(40 mmol/L) and 0.5 mL enzyme. The decomposition of H2O2 was
measured by the decline in absorbance at 240 nm. SOD was
extracted by 100 mmol/L sodium phosphate buffer (pH 6.4). The
reaction mixture (3 mL) contained 50 mmol/L sodium phosphate
buffer (pH 7.8), 13 mmol/L methionine, 75 mmol/L nitroblue tetrazolium
(NBT), 10 mmol/L EDTA, 2 mmol/L riboflavin and 0.1 mL
enzyme extract. The mixtures were illuminated by light (60 mmol/
m2/s) for 10 min and the absorbance was then determined at
560 nm. Identical solutions held in the dark served as blanks.
Protein content was determined according to Bradford (1976) with
bovine serum albumin (BSA) as standard. The enzyme activities
were analyzed once a day for up to 5 days. Each treatment contained
three replications, and 15 fruits were used in each replicate.
The entire experiment was repeated twice.