The Effects And Mechanisms Of Spore-producing Bacteria On Decreasing Heavy Metal Uptake By Two Vegetables

Microbial remedation is a kind of friendly,easy accessibility and cheap technology to remediate heavy metal-polluted soils.Microbes can promote the growth of plants,strengthen the heavy metals tolerance of plants,decrease the biological effectiveness of heavy metals in the soil and reduce the transfer of heavy metals to plants in many ways.Many studies showed that inactivator can absorb the heavy metals in the soil.So,inactivator and microbes may be able to reduce the contents of heavy metals in vegetables which can up to safety standard.The research can ensure the safety of agricultural products,enrich the resources of plant growth promoting bacteria(PGPB)resources and provide technical supports for the improvement of the heavy metal pollution in farmland soil.Twelve strains which can produce indole-3-acetic acid(IAA),siderophore,ACC-deaminase and H2S and possess resistance to multi-heavy metals were screened from two hundreds and sixty-two strains preserving in our lab.The 12 strains above were selected to perform pot experiments using the contaminated soil collected from Qixia Mountain.The biomass and heavy metal contents of the vegetables of Brassica rapa L.Chinensis Group.and Lactuca sativa were detected.The results showed that the 12 strains can increase the aboveground biomass of Brassica rapa L.Chinensis Group.and Lactuca sativa by 6.8%-26.7%and 1.9%-114%respectively,and the root biomass by 11.3%-68.8%and 3.7%-35.2%respectively.Pb,Zn,Cu and Cd concentrations of Brassica rapa L.Chinensis Group.inoculated with the 12 strains were decreased by 15.9%-89.1%,1.3%-46.9%,10.6%-82.8%,8.6%-27.1%,respectively;Pb,Zn,Cu and Cd concentrations of Lactuca sativa inoculated with the 12 strains were decreased by 22.9%-80.1%,21.0%-24.2%,17.1%-34.3%,5.3%-38.5%,respectively.At the same time,the 12 strains can increase the relative contents of chlorophyll of the two kinds of leaf vegetables by 8.7%-34.0%and 2.3%-12.7%,respectively.Strains XL16,XL23,XL108 and H3 all had the characteristics of increasing the biomass,decreasing the content of HMs and increasing the relative contents of chlorophyll.According to the adsorption test,16S rDNA phylogeny status and safety,Bacillus sp.H3 was selected as the main strain of research.The combinations of strain H3 and inactivators(red-mub and biochar)were investigated for getting better efficiency to decrease the contents of HMs in the vegetables.The results showed the combinations of strain H3 and biochar performance was better.The combinations of different concentrations of strain H3 and different concentrations of biochar were tested.Considering the comprehensive factors of biomass,contents of heavy metals,contents of Vc and contents of soluble protein of the edible part of vegetables,the combinations of that the concentration of biochar is 0-2%and the concentration of strains H3 is 5%had the better efficiency.