Strategies Of AM Fungi On Growth And Uptake, Distribution Of Cadmium By Alfalfa (Medicago Sativa L.)

Heavy metal pollution refers to the harmful of heavy metal, which was caused by human activities in soil ecosystem. The heavy metal content in polluted soil was significantly higher than those in natural habitats. Based on the plant growth characteristics, phytoremediation technology has been widely used for bioremediation to polluted environment. Nowadays, screening of heavy metal hyperaccumulation plants has become one of research hotspots in ecology and environment science. On the basis of this, alfalfa (Medicago sativa L.) was selected to test the influence of AM fungi on regulation the heavy metals Cd absorption and distribution strategies.This study included three experiments:1) the difference of native AM fungi and the single exotic AM fungus (Glomus versiforme) on the absorption and distribution of Cd.2) Under different phosphorus level, the influence of a single exotic AM fungus to Cd absorption and distribution in alfalfa.3) Using the microscopic section technology and submicroscopic slicing technique, the distribution of Cd in alfalfa cells and tissues were determined.1) The colonizations of native AM fungi were higher than those of the single exotic AM fungus (G. versiforme). The native AM fungi could promote the host plants tolerance to Cd stress than the single AM fungus. Inoculated with AM fungi can effectively promote the growth of alfalfa and improvement phosphorus nutrition, and native AM fungi effect better than the single AM fungus. Inoculation with AM fungi could increase the amount of mycorrhizal plants enrichment of Cd, and the single AM fungus (G versiforme) is more advantageous to Cd fixed in plant roots, means reducing the parts of the Cd transfer to shoots.2) Under the condition of different phosphorus contents, AM fungi have different influence on the growth of alfalfa. In 20mg·kg-1 phosphorus contents, the colonization rate of AM fungi in Gansu alfalfa is the highest. However, the highest colonization Longzhong alfalfa. AM fungi can significantly promote the growth of Tianshui alfalfa and phosphorus accumulation, but a negative effect to Longzhong alfalfa. AM fungi can significantly increase the Cd absorption and fixation of Tianshui alfalfa.3) Heavy metal Cd deposition sites in alfalfa stems were mainly including phloem, collenchyma and epidermis, pith of lignification area. In the roots of alfalfa, Cd was mainly distributed in catheter, starch grains, or starch granule package. There was no Cd in duct cell wall. Plant tissue lignification seems to inhibit Cd in the xylem area deposition.