The redox state and activity of superoxide dismutase classes in Arabidopsis thaliana under cadmium or copper stress.

The redox state of glutathione and ascorbate as well as the activity of superoxide dismutase classes were determined in leaves of Arabidopsis thaliana grown for seven days in the nutrient solution containing 0, 5 and 50 microM Cd or Cu excess. A decrease in GSH/GSSG ratio was found in plants under Cd and Cu stress. In the plants exposed to Cu stress the activity of all SOD classes increased. However, in the plants treated with Cd the activity of FeSOD and MnSOD was elevated, but CuZnSOD activity was diminished in comparison with control. In these plants the activity of SOD classes was dependent on both the GSH/GSSG and AA/DHA ratios, while in those exposed to Cu excess - on the GSH/GSSG ratio. Differences were shown in the changes both in redox state and activity of SOD classes caused by the metals differing in physiochemical properties. Moreover, relationships between changes in SOD class activities and ROS levels were discussed.