Effect of Cadmium on Antioxidant Enzymes in the Presence of Beneficial Arbuscular Mycorrhizal Fungi: An Incubation Study Using Brassica Juncea (Indian mustard)

Cadmium (Cd) is a Group-B1 human carcinogen, ranked among top ten in 2005 Priority List of Hazardous substances at Superfund sites by the Agency for Toxic Substances and Diseases Registry (ASTDR). Cadmium is dispersed in natural and agricultural environment mainly through anthropogenic activities such as mining, refining, electroplating, municipal waste incinerators, and fossil fuel combustion sources, as well as natural rock mineralization processes. Cadmium is relatively mobile in plants where it can influence mineral nutrition. The symptoms of Cd-toxicity in plants are easily identifiable ranging from slight injury to lethality or crop failure. The most general symptoms are stunted growth, chlorosis, root necrosis and alteration of anatomical, morphological, physiological and biochemical properties of the leaves, stem and roots. Cadmium also affects plant reproduction by inhibiting pollen germination and germ tube growth. The basis of Cd toxicity in biological system lies mainly in its strong affinity for SH-containing ligands. One of the major consequences of Cd toxicity is oxidative stress, mediated by increased levels of reactive oxygen species (ROS). The objective of this study was to gain insight into the biochemical stress response mechanism in Brassica juncea (Indian mustard) treated with inorganic source of Cd in the presence of arbuscular mycorrhizal fungi. Cadmium was used as cadmium nitrate at three different rates: 100, 250 and 500 mg/L respectively. Plants were grown for a month in a temperature and humidity controlled growth chamber. The activities of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT) and Glutathione peroxidase (GPx) in plants treated with Cd were investigated in presence and absence of arbuscular mycorrhizal fungi in one month old shoot tissue.