Effects Of Herbaspirillum Sp. P5-11 And P5-19 On The Growth Of Three Plants On Coal Gangue

The coal gangue produced in the process of mining occupies a large amount of land resources,and its bad physical and chemical properties also threaten the growth of plants and the survival of microorganisms,which leads to serious environmental problems.The plantmicrobial composite remediation technology plays an important role in reducing and enhancing plant resistance,environmental stress and improving landscape in mining areas,and has become one of the effective ways to solve the ecological damage and environmental pollution of gangue hills.Therefore,it has been widely applied in ecological remediation.In this study,two strains isolated from the rhizosphere of Imperata cylindrica were selected as plant growthpromoting bacteria,and the plant growth-promoting characteristics of the two strains were studied.Pure soil,coal gangue mixed with 10% soil,coal gangue mixed with 20% soil,coal gangue covered with 5cm soil and coal gangue covered with 10 cm soil were selected as plant growth substrate.Vetiveria zizanioides,Bothriochloa ischaemum and Indigofera pseudotinctoria Matsum was used as plant inoculation object,2 strains of bacteria were inoculate into 3 plants in 5 substrates,The effects of two strains inoculated for two months on the growth promoting ability and stress resistance ability of three plants were studied,and the most suitable plants were selected.The growth promotion effect of the two strains on Vetiveria,the improvement effect on the substrate and the influence on the rhizosphere microorganism of vetiver were studied after inoculation for one year,and the optimal combination of plantmicrobe-substrate was selected to restore the ecological environment in the mining area.The research results are as follows:Two strains isolated from copper tailings were identified by 16 S r RNA gene sequence and observed by scanning electron microscopy.P5-11 and P5-19 were Herbaspirillum,they were slightly curved rods,and the sizes were(0.2-0.3)?m ×(0.8-1.2)?m.The growth-promoting properties of the strains were determined.They were capable of nitrogen fixation,phosphorus dissolving,indole-3-acetic Acid(IAA)production and siderophore production.The maximum nitrogen fixation capacity of P5-11 and P5-19 was 109.78±3.68mg/L and 107.04±3.72mg/L,respectively;the phosphorus-dissolving ability of both strains was weak,the capacity of P5-19 was about 1.4 times that of P5-11;the IAA synthesis of P5-19 was about twice that of P5-11,and the maximum siderophore-producing content of P5-11 and P5-19 were 7.65±0.26?M and8.60±0.47?M,respectively.Two strains were inoculated on three plants growing on five substrates,and the growth status and stress resistance of the plants were measured.The results showed that Vetiveria and Bothriochloa ischaemum could can survive and grow on coal gangue substrates,but Indigofera pseudotinctoria Matsum could not.The effect of P5-19 inoculation on plants was better under short-term planting conditions,it had better growth promotion effect on Vetiveria,and had a more significant effect on the stress resistance physiology of Vetiveria,in addition,the concentration of heavy metals in Vetiveria was relatively weak,and the tolerance of Vetiveria to heavy metals was better than that of Bothriochloa ischaemum,so the combination of Vetiver and Herbaspirillum was more suitable for the ecological restoration of coal gangue mining areas.One year later,the early inoculation of Herbaspirillum improved the rhizosphere microflora,and it still had a positive effect on nitrogen,phosphorus dissolution and the activity of antioxidant enzymes in Vetiveria.The accumulation of heavy metals in Vetiveria was affected by the improvement of the substrate.Heavy metals were enriched in the upper part of Vetiveria in the gangue mixed soil substrate,and the concentration of heavy metals in the aboveground and underground parts reached a balance in the gangue covered soil substrate.Based on the growth status of Vetiveria and the improvement of the substrate,vetiver planting on the soil gangue substrate has a good effect on the substrate improvement.The combination of Vetiveria planting on the gangue mixture 10% soil substrate with P5-11 and the combination of Vetiveria planting on the gangue mixture 20% soil substrate with P5-19 is more suitable for the ecological restoration of coal gangue mining area.The results of high-throughput sequencing of one year's Vetiveria rhizosphere and root table samples showed that the bacterial diversity and abundance were higher in coal gangue mixing soil substance,and it has more endemic species.On the coal gangue substrate,the improved method and inoculation treatment both affected the composition of bacterial community in the root of Vetiveria,the most significant effect on the community structure of Vetiveria root surface in the coal gangue mixed with 10% soil substrate.To sum up,P5-11 was inoculated on Vetiveria and growing on the coal gangue with 10% soil substance is the optimal combination for coal gangue ecological restoration.It was preliminarily proved that the two strains of Herbaspirillum could provide excellent strains for the development of growth-promoting fertilizer.This paper provides a reference value for the application of the combined restoration of Herbaspirillum-forage grass in the ecological restoration of coal gangue mining areas.In order to maintain the activity of the strain and ensure the efficient symbiosis between the strain and the plant,it is necessary to find a suitable carrier for the application of the strain to a large range of field coal gangue remediation.