Cadmium-induced oxidative damage and antioxidant responses in Brassica juncea plants

Indian mustard (Brassica juncea L. cv. Vitasso) plants exposed to 10, 30, 50 and 100 µM of Cd for 5 d in hydroponic culture were analysed with reference to the distribution of Cd2+, the accumulation of biomass and antioxidants and antioxidative enzymes in leaves. Cd induced a decrease in plant biomass. The maximum accumulation of Cd occurred in roots followed by stems and leaves. Cd induced a decrease in catalase (CAT) and guiacol peroxidase (GPX) activities but an increase in ascorbate peroxidase (APX) and monodehydroascorbate reductase (MDHAR) activities. Enhancement in dehydroascorbate reductase (DHAR) activity was also at 10 µM Cd. Glutathione reductase (GR) activity showed pronounced stimulation after all treatments, but glutathione S-transferase (GST) and glutathione peroxidase (GPOX) activities decreased. The effectiveness of ascorbate-glutathione cycle (AGC) was determined by the ratio of ascorbate to H2O2. This ratio decreased in the Cd-treated leaves which indicated that the cycle was disordered.