Responses of components of antioxidant system in moongbean genotypes to cadmium stress

Four genotypes (Pusa 9531, Pusa 9072, Pusa Vishal, PS-16) of moongbean [Vigna radiata (L.) Wilczek] grown in earthen pots were treated with cadmium at 0, 25, 50, and 100 mg kg(-1) soil. Cadmium tolerance (CdT), the ability of a plant to maintain growth at high levels of cadmium (Cd), was calculated as the ratio of dry-matter production in the untreated and the Cd-treated soils. The moongbean genotypes showed a differential response to Cd concentrations; Pusa 9531 was identified as Cd tolerant, whereas PS 16 was Cd susceptible. To find out the physiological basis of these differences, we investigated the possible role of antioxidant (enzymatic and nonenzymatic) defense systems. Activities of superoxide dismutase (EC 1.15.1.1), catalase (EC 1.11.1.6), ascorbate peroxidase (EC 1.11.1.11), and glutathione reductase (EC 1.6.4.2) and the amounts of ascorbate and glutathione were monitored in the Cd-tolerant and Cd-sensitive moongbean genotypes. The results revealed the presence of a strong antioxidant defense system in the Cd-tolerant genotype (Pusa 9531) for providing adequate protection against oxidative stress caused by Cd.