d2+胁迫对竹叶眼子菜的生理特征和超微结构的影响

The toxic effects of different gradient concentrations of Cd2+ (0, 2, 4, 6 and 8 mg L-1) on chlorophyll content, anti-oxidase system, MDA content, soluble sugar content, soluble protein content and ultrastructure of the cells of Potamogeton malaianus were studied. With Cd2+ increasing, the chlorophyll content, soluble protein content and the activity of superoxide dismutase (SOD) decreased drastically, while the MDA content and soluble sugar content increased. The activities of catalase (CAT) and peroxidase (POD) increased, and when reached at 2 mg L-1 they decreased then. Glutathione (GSH) and ascorbic acid (ASA) content increased, and decreased after 4 mg L-1. SDS-PAGE revealed that Cd2+ reduced the amounts of four polypeptides with apparent molecular weights as 52.1×103, 42.9×103, 27.4×103 and 14.1×103, respectively, while it promoted the expression of one polypeptide with apparent molecular weight 18.1×103. Ultrastructural observation showed that the ultrastructural damage was much more serious at higher pollutant concentration. This resulted in swelling of chloroplast, disruption and disappearance of chloroplast membrane, disintegration of chloroplasts, dilatation of cristae, deformation and vacuolization of mitochondria, condensation of chromatin in nucleus, dispersion of nucleolus, and disruption of nuclear membrane and nucleoplasm flowing into cytoplasm. Generally, the response of SOD, chlorophyll and soluble protein was most sensitive to Cd2+ toxicity, which could be recommended as bio-monitoring indicator of Cd2+ pollution in water body. The EC50 of Cd2+ to P. malaianus was 2.97 mg L-1 based on the experiment results.