Malondialdehyde (MDA) measurement was carried out by the method of Heath and Packer (1968), with a slight modification. Fresh peel tissue (2.0 g) from ten fingers was homogenized in 10 mL of 10% trichloroacetic acid, and centrifuged at 10,000 × g for 20 min. The supernatant was collected, and 1 mL of it was mixed with 3 mL of 0.5% thiobarbituric acid. The mixture was boiled for 15 min, then quickly cooled in an ice bath and centrifuged at 12,000 × g for 15 min. The supernatant was collected and used to measure absorbance at 450, 532, and 600 nm. The MDA concentration was calculated according to the formula: 6.453 × (A532 − A600) − 0.563 × A450. The concentration of MDA on a fresh weight basis was calculated mmol kg−1.