Effects of arbuscular mycorrhizal fungi on heavy metal tolerance of clover in contaminated soil

The effects of arbuscular mycorrhizal fungi (AMF) on Cu，Zn，Pb and Cd uptake and distribution in red clover plant were investigated by using a four-compartment culturing system under greenhouse conditions. Cu(CuSO₄·5H₂O)100mg/kg，Zn(ZnSO₄·7H₂O)600mg/kg，Pb［Pb(NO₃)₂］300mg/kg，Cd(CdSO₄·8H₂O)10mg/kg were added to loamy soil which was precultured for one month before sowing clover seeds. The growth of red clover is observed not to be impeded in the heavy metal contaminated soil，while inoculation rates of two AMF species Glomus intraradices and Glomus caledonium are significantly decreased by 53% and 56% respectively and hypla density of Glomus intraradices is decreased by 73%. AMF still significantly decreases the uptake of Cu，Cd and Pb，and prevents transportation and distribution of heavy metals in the shoot systems of the clover plants. The concentrations of Pb，Cd in the clover shoots decrease by 24.2%～55.3% and 65%～97.9% respectively，compared with non-inoculated clover,below the upper limits of the standards of animal feed in China. It is concluded that AMF can increase clover quality and benefit field treatment of sewage one the hand，and limit contaminants uptake through food chain on the other. AMF plays a crucial role in regulating Cu，Zn and，especially Pb，and Cd bio-recycling in the ecosystem and in alleviating the stress and transfer of heavy metals along food chain.