Studies On The Effects Of Arbuscular Mycorrhizal Fungi On Plant Chromium Tolerance

Arbuscular mycorrizal fungi(AMF)that can form symbiotic association with the majority of terrestrial plants are ubiquitous in the soil.It has been well demonstrated that AMF can assist plant to adapt to heavy metal stress,and are potentially valuable for phytoremediation or ecological restoration of metal contaminated soils.The present study conducted two pot experiments to explore the effects of AMF on different plants chromium tolerance.The key findings are as follows:(1)Biochar as a new sorbent,which characterized by high porosity,large specific surface area,abundant functional groups and high surface charge density,that it can improve soil quality and reduce the migration and bioavailability of heavy mental in soil.A pot experiment was carried out to investigate the effects of the interaction between AMF inoculation and rice husk biochar application(0,1.5%,3%,5%)on Medicago sativa growth,absorption and accumulation of chromium under 15mg/kg Cr(Ⅵ).The results indicated that,under Cr(Ⅵ)stress,either AMF inoculation or biochar application alone significantly increased alfalfa biomass,decreased Cr concentration of shoot and root,as well as chromium transport coefficient.Combining AMF and biochar has the best effect on promoting plant growth and inhibiting Cr absorption as well as transport.In general,this effect was better with the increase of biochar concentration.The biomass,shoot Cr concentration and Cr transport coefficient of AMF inoculation and 5%biochar trentment were 84.5,0.08 and 0.2times of without AMF and biochar trentment,respectively.The gradual regression analysis shows that acid extractable Cr is most effective to plants.AMF inoculation or biochar application significantly decreased acid extractable Cr concentration,therefore reduced chromium phytotoxicity.In addition,biochar application significantly increased the soil available phosphorus to create a better environment for plant growth.(2)Leersia hexandra Swartz as a chromium hyperaccumulator,has great potential in the remediation of Cr pollution.A pot experiment was conducted to explore the effect of AMF on Leersia hexandra Swartz growth,absorption and accumulation of Cr.The results indicated that,mycorrhizal colonization was low.In general,AMF inoculation significantly increased shoot biomass,but had no significant effect on shoot Cr concentration and Cr transport coefficient.This study has demonstrated that combining AMF and biochar increased plant Cr tolerance by promoting plant growth and inhibiting Cr uptake,that provide a valuable technical approach for the safe utilization of Cr contaminated soil.However,as Gramineae,AMF inoculation has no significant effect on improving chromium tolerance of Leersia hexandra Swartz.