Research On Alleviation Of Cadmium Stress On Aquatic Plants By Rare Earth Neodymium

In this paper we studied the photosynthetic systems, protective enzyme systems, content of cadmium and mineral elements and ultrastructurer of Potamogeton crispus L. and Elodea Canadensis L. under Cd²⁺, Nd³⁺ and their combined treatment , by the mean of measurement of physiological parameters, observations of electron microscopy as well as measurement of concentration of elements(ICP-MS method). Result of the test indicated that treatment of single Nd³⁺ on Potamogeton crispus L. improved the photosynthetic efficient, enhanced the activities of antioxidase system(SCD, CAT, POD) and reduced the generation of MDA. The plant showed the vigorous vitality. By the treatment of single Cd²⁺, no matter in Potamogeton crispus L. or in Elodea Canadensis L., the chlorophyll content and soluble protein content dropped, antioxidase activity reduced notably , membrane lipids were peroxidated, MDA content rised , and as the result plants died gradually. Addition of different concentrations of Nd³⁺ alleviated the toxic symptom of plant under Cd²⁺ stress, which could be expressed in these ways:(1)Treatment of Nd³⁺ improved the chlorophyll content of Potamogeton crispus L. under Cd²⁺ stress, and chloroplast structure was kept integrity;(2) The activities of antioxidase system were raised and the ability of scavenging the free radical was enhanced, MDA content reduced;(3) Ion content in plant deviated from normal value under Cd²⁺ stress, but addition of Nd³⁺ made some ions become normal, however was not helpful to all ions;(4) Cadmium content in Elodea Canadensis L. under Cd²⁺ stress dropped with treatment of Nd³⁺ compared with single cadmium. Alleviation mechanism of rare earth neodymium to the damage of aquatic plants by heavy metal cadmium was discussed primarily on the base of experimental result.