MOLECULAR AND PHYSIOLOGICAL ASPECTS FOR Lepidium sativum TOLERANCE IN RESPONSE TO LEAD TOXICITY

The present study was undertaken to evaluate the toxicity of Pb2+ on photosynthetic pigments, total soluble protein and MDA contents as well as the activities of SOD, CAT and POD in Lepidium sativum leaves after 10-days of supplying lead (0-600 ppm) in the nutrient solution. The results indicated that lead treatment adversely affected plant growth and disturbed the cell metabolism critically. The development of toxic symptoms, corresponding to a high accumulation of Pb2+, was a sum of the increase in H2O2 and MDA contents, decrease in protein content, and the much elevated SOD and POD activities in leaves. In addition, the results demonstrated that exposure to high lead concentration (Pb2+ >400 ppm) could result in the disintegration of antioxidant system in Lepidium seedlings. Also the significant decrease in the contents of photosynthetic pigments was related to high-level metal stress. Higher concentrations of Pb2+, especially 400 and 600 ppm, resulted in a great variation in protein pattern distribution, migration position and bands intensities. The outcome of this study corroborates that Lepidium sativum is a suitable hyper-accumulator candidate and tolerant against low-level lead contaminated soil.