Effects Of Two Herbaspirillum Strains (P5-11 And P5-19) On The Growth Of Three Plants On Copper Tailings

Tongling has a long history of mineral resources exploitation,the solid mining waste tailings produced in the process of mining occupies a large amount of land resources.Long-term wind erosion and rain leaching caused heavy metals such as manganese(Mn),copper(Cu),zinc(Zn),cadmium(Cd)and lead(Pb)in the tailings to pollute local farmland and groundwater,causing a series of environmental problems.It has very important practical significance for the remediation and management of tailings in this area.In this study,five kinds of plant growth substrates include copper tailings,two kinds of mixing soil treatments(adding 10% and 20% uncontaminated soil in the tailings according to the mass ratio)and two kinds of covering soil treatments(covering 5 cm and 10 cm uncontaminated soil on the tailings)were setted,a 60-day plant pot experiment was carried out,and the effects of Herbaspirillum sp.P5-11 and Herbaspirillum sp.P5-19 on the growth physiology,heavy metal accumulation and transport of Vetiveria zizanioides,Coreopsis drummondii and Bothriochloa ischaemum in the substrates were studied,then the potential effects of two strains of Herbaspirillum sp.and the alien soil improvement on phytoremediation of copper tailings were discussed.The main results are as follows:(1)The biomass and plant height of three kinds of plants were significantly increased by two strains of Herbaspirillum sp.,and the inoculation of Herbaspirillum sp.P5-19 combined with the covering 10 cm soil improvement was the most beneficial to the growth of the plants in the tailings.Inoculating increased the content of photosynthetic pigments in Vetiveria zizanioides and Coreopsis drummondii,but inhibited the synthesis of photosynthetic pigments in Bothriochloa ischaemum(Chlorophyll a,chlorophyll b and carotenoids decreased by 2.59-22.56%,1.96-26.78% and 2.31-27.86%,respectively).(2)The content of Malondialdehyde(MDA)in plants was decreased by inoculation and soil improvement.All the four kinds of alien soil improvement could alleviate the stress of heavy metals on plants.The activities of Superoxide Dismutase(SOD),Peroxidase(POD)and Catalase(CAT)in Vetiveria zizanioides,Coreopsis drummondii and Bothriochloa ischaemum were all decreased.The activities of antioxidant enzymes of the three plants were significantly increased after inoculation with growth-promoting bacteria P5-11 and P5-19,which effectively enhance the tolerance of plants to heavy metals.(3)After inoculation with plant growth-promoting bacteria P5-11 and P5-19,the content of heavy metals Mn,Cu,Zn,Cd and Pb in the three plants were significantly increased.Covering 10 cm soil improvement combined with inoculation P5-19 treatment had a better effect on the extraction of heavy metals,and the translocation factor of heavy metals in these plants were increased distinctly.(4)Inoculation increased the abundance and diversity of microorganisms,affected the change of microbial community structure,improved the microenvironment of plant growth,and promoted plant growth and the extraction of heavy metals.The results showed that the two strains could effectively improve the growth physiology and heavy metal absorption capacity of the three plants under copper tailings stress,Vetiveria zizanioides with P5-19 combined with copper tailings covering 10 cm of soil and Coreopsis drummondii inoculation with P5-19 combined with copper tailings mixed 20% of soil were effective restoration modes suitable for tailings ecological remediation,which further provided scientific basis and technical support for ecological remediation of mining areas.