The effect of Cd on mycorrhizal development and enzyme activity of Glomus mosseae and Glomus intraradices in Astragalus sinicus L.

The influence of cadmium (Cd) on the root colonization of Astragalus by two arbuscular mycorrhizal fungi (AMF) was investigated. Astragalus sinicus L. grown in the soil in the presence of four levels of Cd was inoculated individually with Glomus mosseae, Glomus intraradices, or by a mixed inoculum of these two fungi. Histochemical vital stains were used to measure the efficiency and function of the mycorrhizal symbiosis after 7weeks. Nested PCR with ALP-active stained roots was applied to monitor the efficiency AMF in mixed community at the same time. The addition of Cd slightly decreased plant biomass and mycorrhizal colonization, and depressed the activities of alkaline phosphatase (ALP) and succinate dehydrogenase (SDH), especially in G. intraradices. Mycorrhizal colonization significantly improved plant growth regardless of the level of addition of Cd. The plants inoculated with G. mosseae or mixed inoculum immobilized more Cd in the roots, and partitioned less Cd to the shoots at the highest Cd addition level. Root colonization efficiency of G. intraradices was improved in the mixed community and G. mosseae was the dominant colonizer in this community. Based on the higher Cd tolerance of this strain of G. mosseae, it would be preferred for bioremediation in Cd contaminated soil.