Lead and copper-induced changes on malondialdehyde, proline, peroxidase and catalase enzymes activity in Portulaca oleracea L.

Portulaca oleracea L. belongs to Portulacaceae order. From the physiological point of view, P. oleracea L., generally known as ragwed, has a very high tolerance and compatibility to the environments polluted with salts or heavy metals. It is considered as a suitable species in planting as well as in refining soil and environment from these kinds of stresses. According to these contexts and in order to show the effects of two heavy metals, lead and copper, on malondialdehyde, proline and antioxidant enzymes activity some experiments were performed in a completely randomized design. For this purpose, plants were planted in sterile bed, leca, irrigated with Hogland nutrient solotion. Treatments included different concentrations of Pb (NO3)2 and CuSO4.5H2O (0, 10,50,100,500,1000 and 1500 µM) with three replications. After ten days of treatment, plants were harvested for experiments. According to the results, an increased absorption of lead and copper was recoreded at high concentrations compared to the control treatment. The amount of atomic absorption of these two elements in roots was more than that of shoots. Stress increased significantly at high concentrations compared to the control. The amount of proline showed a significant upward trend in both lead and copper stress as well as in both roots and shoots. Peroxidase activity showed a significant upward trend in both lead and copper stress as well as in both shoots and roots while a significant downward trend was recorded for catalase activity. In general, a higher amount of malondialdehyde, proline and peroxidase activity was obtained in root samples comperd to shoot samples, indicating the role of root as the main accumulator of heavy metals, lead and copper. The lower catalase activity in roots compared to shoots proved enzyme sensitivity towards high Pb and Cu accumulation in roots.