The Construction Of Multi-functional Microbiota And Its Application Of Castor In Phytoremediation Of Lead And Zinc Soil Contamination

Phytoremediation of heavy metal contaminated soil is recognized as one of the most effective methods of low cost,environment friendly and no secondary pollution.However,plants currently used for restoration tend to have low survival rates,slow growth and low biomass.The application of plant-microbial joint remediation technology for heavy metal contaminated soil can improve the efficiency of phytoremediation,and has become one of the focuses of the current researches.A large number of studies show that a single microorganism has relatively poor stability,and is difficult to compete with indigenous microorganisms,resulting in slow repair efficiency.Meanwhile,plant-promoting strains can fix nitrogen,dissolve phosphorus,and secret plant hormones(i.e.IAA,ACC,and etc.)which altogether can effectively alleviate plant heavy metal toxicity and improve plant resistance.Combined with the above characteristics,it is a new trend to construct an efficient microbiota with relatively stable ecological structure and comprehensive function.It has been shown that combining rhizosphere microorganisms of different functional types is more beneficial to enhance the remediation effect of composite heavy metal contaminated soil.Therefore,this study isolated and screened 78 microorganisms from the rhizosphere soil of lead and zinc tailings,and through minimum inhibitory concentration(MIC)test,physiological and biological properties and antagonistic experimental analysis,then selected five strains to build a multi-functional microbiome(M),and inoculated multi-functional microbiome in Ricinus communis L roots,investigated multi-functional microbiome to strengthening the phytoremediation effect of Ricinus communis L on lead and zinc contaminated soil.The results of this test show that:(1)With the increase of soil heavy metals,the content of acid extraction in soil increased,the combined(MB)ratio of multi-functional complex microbiota and biochar were added separately,the acid extractable heavy metal were high in the processing group of multi-functional microbiome and biochar(B),and the multi-functional microbiome promoted the absorption of heavy metals by activating heavy metal ions.(2)After different treatments,the root system developed MB>M>B>CK(natural soil);In different concentrations of single heavy metal stress,the phenomenon of"low-promoting high suppressions" appeared,and the Pb treatment had the best root development at 300 mg/L,and plant had the best root development at 200-400 mg/L of Zn stress;(3)Adding M and B can change soil nutrients and structures so that to improve the biomass of castor,and in the same concentration treatment group,adding M is better than adding B.(4)The addition of multi-functional microbiota improved the heavy metal content in plant body,and the absorption content of Zn on plant land is significantly higher than that of Pb,which showed that the addition of multi-functional microbiota improved the ability of plant above-ground part to absorb heavy metal,and Zn’s transport capacity is stronger than that of Pb.(5)The composition of the rhizosphere microbiome was determined by the complex interaction between the non-biological environmental factors and their interactions,and adding M and B can change the number of different microorganisms in the indigenous microbiota,reduce the number of primary dominant species and increase the number of other species.