Effects of Cd, Cu, Pb, and Zn Combinations on Phragmites australis Metabolism, Metal Accumulation and Distribution

In this study the effects of heavy metals were investigated in Phragmites australis plants. Effects of different concentrations of Zn (30.6, 76.5 mu M), Cu (31.5, 78.7 mu M), Cd (4.4, 17.6 mu M) and Pb (10.0, 22.5 mu M), simultaneously applied to the seedlings, were detected by measuring changes in their concentrations, antioxidants enzymes, chlorophyll, soluble proteins and free amino acids. Concentration of Zn and Cu increased maximally in stems, whereas Cd and Pb increased maximally in roots as compared to other plant parts. The percentage increments were highest for Cd followed by Zn, Cu and Pb. In this study, increased free radical generation was found in P. australis plants under heavy metal stress as indicated by the high malondialdehyde (MDA) production. MDA content in the leaves depends, as well, on the type of heavy metal whose concentration increased. Superoxide dismutase, catalase, ascorbate peroxidase, glutathione peroxidase and peroxidase activity in P. australis leaves increased significantly with the increase in heavy metal concentration. The exposure to Zn, Cu, Cd and Pb decreased significantly soluble protein and chlorophyll contents and altered greatly the composition and concentration of the free amino acids. The presence of high concentration of Cd in the nutrient solution resulted in the maximum reduction of soluble protein content.