. Determination of indices of oxidative damage
Lipid peroxidation in the leaves of each test sample was determined by thiobarbituric acid reactive malondialdehyde (MDA) production following the method of Heath and Packer (1968).
Intactness of plasma membrane in leaves was measured as the leakage percentage of electrolytes as described by Gong et al. (1998).
Fresh leaves (200 mg) were washed thoroughly with deionized water, cut into pieces of 5 mm length and placed in test tubes containing 30 ml deionized water at 30 8C for 2 h.
To measure the EC, two sets of treated and untreated samples were taken.
First set of the samples were centrifuged, and the initial electrical conductivity of the supernatant (EC1) was measured using digital conductivity meter (CC–607, Century, India).
Second set of sample was boiled at 100 8C for 15 min to release all electrolytes, cooled and centrifuged, and final electrical conductivity (EC2) of supernatant was measured.
The leakage percentage of electrolytes was calculated by using the formula (EC1/ EC2) _ 100.