摘要：The phytoremediation of heavy metals is widely used in the remediation of cadmium-contaminated sewage water and soil. Hydrilla verticillata can potentially be applied in heavy metal bioremediation. To understand the tolerance and maximize the potential application of H^drilla verticillata in bioremediation, we conducted aqueous solution assays of antioxidant enzymes and cadmium (Cd) bioaccumulation in Hydrilla verticillata when these plants were cultured under different Cd concentrations (1~32 ^M) for 2, 4, 6 and 8 days. These plants were selected and assayed for changes in the antioxidant enzymes catalase, superoxide dismutase, malondial-dehyde, peroxidase and polyphenol oxidase. Our results show that Cd toxicity may affect the production of MDA and change antioxidant system enzymes in the leaves and stems of Hydrilla verticillata. These changes were related to cadmium concentration and treatment time. The maximum accumulated cadmium of Hydrilla verticillata was significantly (P<0.05) affected by the cadmium concentration and treatment time. The tolerance concentration of Hy-drilla verticillata for Cd toxicity was 20 under the experimental conditions. The up-regulation of antioxidant enzymes may enhance the tolerance of Hydrilla verticillata in Cd polluted water. The results suggest that Hydrilla verticillata exhibits a strong tolerance within the tolerance threshold cadmium concentration range over limited treatment times. These findings will help to clarify the process of accumulation in submerged plants and establish a scientific and economical restoration programme for different concentrations of heavy metals in polluted water; it will further provide a good theoretical basis for heavy metal remediation.
关键词：Heavy metal pollution;H-ydrilla verticillata;antioxidant enzyme;tolerance mechanism;Cd accumulation
