Growth, nitrate reductase activity and antioxidant system in cadmium stressed tomato (Lycopersicon esculentum Mill.) cultivars

Ten cultivars of tomato were subjected to different cadmium (Cd2+) concentrations, to find out their degree of tolerance towards these metal ions during the tomato ontogeny. Seeds of tomato cultivars (i.e. `K-25', 'K-21', 'NTS-9', 'Kaveri', 'NBR-Uday', 'Swarnodya', 'Sarvodya', 'NBR-Uttam', 'Malti' and 'S-22') were soaked in 0, 50, 100 or 150 mu M of Cd2+ for 0, 4, 8 or 12 h. Despite substantial varietal differences, increases in Cd2+ concentration and the soaking duration caused a linear decrease in growth and a reduced activity of catalase and peroxidase for all varieties. Variety 'K-25' was found to be the most resistant cultivar as it possessed maximum activity of antioxidative enzymes reflecting one of the possible reasons to overcome stress conditions. However, the seeds of 'S-22' could not germinate in the presence of even the lowest Cd2+ concentration.