[Comparative research on Cd removal from water by different kinds of seedlings]

Ecological effects of Cd removal from water and the changes of physiological and biochemical indexes of seedlings of maize, sunflower and castor-oil plant were investigated. The results showed that (1) with the trial time lasting, Cd content in solution decreased, and the processes of Cd removal by seedlings of each concentration were almost completed in 48 hours. The removal effects of sunflower and castor-oil plant were better than those of maize at 1 mg x L(-1) and 2 mg x L(-1) Cd, whereas the best removal effects at 5 mg x L(-1) and 10 mg x L(-) Cd were those of castor-oil plant, followed by maize and sunflower. (2) Root absorbed the most proportion of Cd by all these three kinds of seedlings at every treatment. The ability of Cd accumulation by the three kinds of seedlings could be drawn as follow sunflower> castor-oil plant > maize. (3) The physiological and biochemical indexes of seedlings exposed to Cd for 72 hours had changed to different degree compared with control. The root activity and the proline content of sunflower both have significant relations with Cd accumulation, and the plasma membrane permeability and the proline content of castor-oil plant both have significant positive relations with Cd accumulation. Maize, sunflower and castor-oil plant could endure certain concentration of Cd, and the tolerance of sunflower and castor-oil plant are both greater than that of maize through general analysis of Cd accumulation and the changes of physiological and biochemical indexes.