Effect of Arbuscular Mycorrhizal Fungi on Uptake and Distribution of Cadmium in Lolium L.

For understanding the leading mechanism of arbuscular mycorrhizae (AM) mediated alleviation of cadmium phytotoxicity, and investigating on the possible application of mycorrhizal symbiosis in bioremediation of contaminated soils, the role of arbuscular mycorrhizae in metal translocation from soil to plant was studied under simulated contaminations on a sandy loam soil. Mycorrhizal effects on plant growth and Cd uptake by Lolium L. inoculated with AM fungi Glomus mosseae, Glomus intraradices were determined in pot experiments under three Cd addition levels (0,15,50 mg·kg-1). Plants were harvested three times at 70 d, 105 d and 210 d respectively after sowing. Only shoots were reaped at the first and second harvests, but both shoot and root were harvested at the third time. These two AM fungi showed some endurance to Cd contamination in soil, since the addition 50 mg·kg-1 Cd in soil didn't decrease mycorrhizal colonization. P concentration in shoot of ryegrass plant was not significantly affected by inoculation with AM fungi, so did the dry weights of ryegrass plant, implying low mycorrhizal dependency of ryegrass on AM fungi. In Cd contaminated soils, AM fungi didn't increase Cd concentration in shoot, but strengthened the bio-fixing of Cd in root and reduced Cd translocation from root to shoot. The distribution proportion of Cd in mycorrhizal plants shoot was lower than that of non-mycorrhizal plants. AM fungus could adjust the distribution proportion of Cd in host plant and protect host plants against heavy metal contamination. These functional characters of AM fungi could play a great role in the melioration and the quality keeping of Cd contaminated pasture soil.