INFLUENCE OF CADMIUM STRESS ON GROWTH, ULTRASTRUCTURE AND ANTIOXIDATIVE ENZYMES IN POPULUS 2025

To understand phytoremediation capability, ultrastructural alteration, and the role of antioxidative enzymes in Populus 2025 (Populus euramericana) stressed by Cd, a hydroponic culture was performed. P. 2025 was treated with 50-500 mu M Cd. The results indicated that 500 mu M Cd significantly inhibited the cultivar (P < 0.05). P. 2025 has considerable ability to accumulate Cd; therefore, 50 mu M Cd does not exhibit significant cellular damage to root cells. Visible symptoms of Cd toxicity were that small vesicles containing electron-dense granules in cytoplasm and vacuolization. But, 100 mu M Cd could induce a series of cell structure injuries, such as increased vacuolization, reduction of mitochondrial membranes, condensation of cytoplasm and chromatin, and led to severe plasmolysis and, finally, to membrane damage and cell death. Under Cd stress, superoxide dismutase (SOD) activity in leaves and roots was found to be high significantly (P < 0.05). Peroxidase (POD) activity in leaves was noted to be low, but catalase (CAT) activity increased. In roots, POD and CAT activities showed increasing trends. The high contents of malondialdehyde (MDA) in the investigation suggested that Cd exposure might lead to more ROS in P. 2025, which could be efficient as phytoextraction plant with considerable ability to accumulate Cd.