For assessment of ascorbic acid, 0.5 g leaf sample was
homogenized in extraction solution of oxalic acid and Na EDTA.
After centrifugation, 5 ml of 2,6-dichlorophenolindophenol
(DCPIP) was added to the supernatant and absorbance of pink
color was measured at 520 nm. The pink color was then bleached
by adding a drop of 1% ascorbic acid and absorbance was taken at
same wavelwngth. The difference between the two measurements
was used to determine the amount of ascorbic acid (Keller and
Schwager, 1977).