[Physiological effects of cadmium stress on Astragalus membranaceus seedlings and alleviative effects of attapulgite clay on cadmium stress].

In this study we investigate the effects of cadmium stress on Astragalus membranaceus seedlings and the alleviative effects of attapulgite clay in growth substrate on cadmium stress to A. membranaceus seedlings. The results showed that the Y (Ⅱ) (effective photochemical quantum yield of PSⅡ photosynthetic), qP(photochemical quenching coefficient), ETR(the rate of non-cyclic electrontransport through PSⅡ), and chlorophyll content of the leaves were significantly decreased with the increase of cadmium concentrations, while the cadmium content, non-photochemical quenching(NPQ, qN) of the leaves and cadmium content, MDA content, plasma membrane permeability, and the damage degree of root apical membrane of the roots were significantly increased. Simultaneously, the activities of APX(ascorbate peroxidase), SOD(superoxide dismutase), POD(peroxidase), CAT(catalase), soluble protein content, and soluble sugar content of roots were increased first but then decreased with the increasing cadmium concentration. Under the condition of without Cd stress, the attapulgite clay into the growth substrate did not significantly affect above physiological indexes of leaves, but significantly increased SOD activity and soluble sugar content of roots and decreased the MDA content, damage degree of root apical membrane of roots, while other physiological indexes did not significantly change. Under cadmium stress, the presence of attapulgite clay in the growth substrate significantly alleviated the cadmium-induced decreases Y (Ⅱ), qP, ETR and chlorophyll content of leaves, and the CAT activity, soluble protein content, and soluble sugar content of roots. Under condition with cadmium stress, the presence of attapulgite clay significantly alleviated the cadmium-induced increases of leaves cadmium content, qN and NPQ, and the cadmium content, MDA content, plasma membrane permeability, damage degree of root apical membrane, SOD, POD, and APX activity of the roots. And, the alleviative effects of attapulgite clay on cadmium stress to A. membranaceus roots were more obvious with the increase of cadmium stress time. The above results showed that the addition of attapulgite clay into the growth substrate has certain alleviative effect on the cadmium stress to A. membranaceus seedlings.