Effect Of Arbuscular Mycorrhizal Fungi On Growth And Microbial Community In Rhizosphere Soil Of Maize Seedlings Grown In La-Contaminated Soils

Overexploitation of rare earth earths（REEs）and widespread application in industry and agriculture have caused to the accumulation of REEs in soil.Former research shows that REEs have a potential risk to the human body and ecosystem.Therefore,it’s imperative to repair and control the soil contaminated by REEs.Phytoremediation is an environmentally friendly and cost-effective approach for soil remediation.However,the plants were limited even died in mining tailing area or the soil contaminated by high concentration of REEs.AM fungi（AMF）can alleviate the toxicity of heavy metals on plant by affecting rhizosphere microorganisms.However,it’s unclear and ambiguous that the effects of AMF on plant rhizosphere microorganisms and its roles on plant resistance under REE stress.A greenhouse pot experiment was conducted to investigate the effects of AM fungi（C.etunicatum）on AM colonization rate,mycorrhizal dependency,plant growth,soil enzyme,soil chemical properties,La uptake and translocation,rhizosphere bacteria and fungi diversity and community of maize（Zea mays L.）grown in soil spiked with Lanthanum（one of the typical REEs in rare earth ores）at 0,10,100,and 500 mg·kg^-1（La0,La10,La100 and La500）.Results indicates that:（1）The average AM colonization rate of maize inoculated with C.etunicatum ranged from 29.47%to 62.83%in different La-contaminated soils.The AM colonization rate was decreased significantly by 34.7%and 53.1%in La100 and La500,respectively.However,mycorrhizal dependence was increased significantly by 347.95%and 359.30%in La100 and La500,respectively.（2）With AMF inoculation,the biomass and nutrient content of maize were increased significantly by 18.46%⁴68.84%and 13.77%⁴41.77%in different La-contaminated soil.Shoot La concentration of maize was decreased significantly by51.53%.Soil organic carbon were increased significantly by 10.55%in La100.La0,La100 and La500 increased significantly net photosynthetic rates of maize by 18.25%and 35.15%,respectively.La0 and La10 increased significantly rhizosphere soil urease activities of maize by 93.62%and 56.94%,respectively.（3）With or Without AM inoculation,Proteobacteria（33.28%⁴6.92%）and Ascomycota（57.84%⁹3.72%）are dominant bacteria and fungi in rhizosphere of maize in different La-contaminated soils.La500 decreased significantly the diversity of maize rhizosphere bacteria.AMF decreased significantly the diversity of maize rhizosphere bacteria and fungi in La0,but increased the diversity of maize rhizosphere bacteria in La500.La500 and AM fungi can affect significantly the structure of rhizosphere bacterial and fungi community.（4）AMF can promote the enrichment of beneficial bacteria Planomicrobium,Lysobacter,Microbacterium,Streptomyce,Actinobacteria Saccharibacteria,Microbacterium and Streptomyces and fungi Penicillium in La500.（5）AM fungi could promote the enrichment of bacteria Planomicrobium to increase the available K and P in the soil,and promote the enrichment of bacteria Lysobacter,Microbacterium,Streptomyce and fungi Penicillium to increase available P in soil and thus promote the growth of plants in La500.The experiment demonstrated that AMF promote the enrichment of beneficial bacteria and fungi in rhizosphere soil of maize and increase organic carbon content in soil to improve the absorption of mineral nutrients,the net photosynthetic rate of plants,the uptake and transport of rare earth elements.These mechanisms enhance plant resistance to REEs and promote plant growth.The results can provide scientific basis for plant-microbial combined remediation of rare earth mining areas and rare earth elements contaminated soils.