Effects Of Endophyte Inoculation On Phosphorus Accumulation And Rhizosphere Characteristics Of Mining Ecotype Polygonum Hydropiper

Phosphorus is an essential nutrient element for plant growth.The application of large amount of phosphorus fertilizer in agricultural production accelerates the accumulation and migration of phosphorus in soil.Mining ecotype Polygonum hydropiper has strong P enrichment ability,which can be used to extract excessive phosphorus from soil environment.Plant endophytes can cooperate with plants to extract pollutants from the environment and effectively improve the efficiency of plant extraction and remediation.Six strains of endophytic bacteria with growth promoting potential of P.hydropiper were obtained in the previous study of the research group,but the effect of inoculation of endophytic bacteria on the growth and phosphorus accumulation of P.hydropiper is not clear.Therefore,in this study,the mine ecological P.hydropiper was selected as the research object to explore the effects of inoculating6 strains of endophytic bacteria on the growth,phosphorus accumulation and rhizosphere environment of P.hydropiper under different phosphorus treatments.The main findings are presented as follows:1)Under high phosphorus condition,the biomass of P.hydropiper was significantly increased by inoculating Pseudomonas plecoglossida SLr02,Kocria sp.SLr15,Bacillus subtilis SLs13 and Arthrobacter sp.SLs18.Compared with the non inoculation treatment,the phosphorus content in shoots of P.hydropiper inoculated with SLs18 increased by 27.61%.After inoculated with endophytic bacteria SLr15,SLs13,SLs18 and SLr02,the accumulation of phosphorus in the shoot of Polygonum hydropiper increased by 610.81%,387.57%,319.46%and 240%.SLr02,SLr15,SLs13 and SLs18 can be used as potential growth promoting bacteria to extract phosphorus from soil.2)Endophytic bacteria P.plecoglossicida SLr02,Kocria sp.SLr15,B.subtilis SLs13 and Arthrobacter sp.SLs18 can dissolve insoluble inorganic phosphorus such as tricalcium phosphate,aluminum phosphate and iron phosphate,especially for tricalcium phosphate.Moreover,strain SLr15 has the strongest ability to dissolve tricalcium phosphate,and the amount of phosphorus can reach 97.40 mg L^-1.The total amount of organic acids in tricalcium phosphate culture medium after inoculation was significantly higher than that in aluminum phosphate and iron phosphate treatment.The secretion of organic acids is one of the mechanisms of dissolution of tricalcium phosphate by endophytic bacteria.3)Under the treatment of tricalcium phosphate and aluminum phosphate,inoculation of B.subtilis SLs13 promoted the growth,root morphological development and phosphorus absorption of P.hydropiper;at the same time,the content of available phosphorus in rhizosphere soil of P.hydropiper was significantly increased,and the content of Ca₂-P was significantly positively correlated with the content of available phosphorus,indicating that the inoculation strain SLs13provided effective phosphorus source for P.hydropiper and promoted P absorption by P.hydropiper through increasing Ca₂-P in rhizosphere soil.P.plecoglossicida SLr02 was inoculated with iron phosphate promoted the growth and root morphology of P.hydropiper.At the same time,the content of available phosphorus in rhizosphere soil of P.hydropiper was significantly increased,soil p H was significantly decreased,and organic acid secretion was significantly increased,which indicated that SLr02 could reduce soil p H,increase available phosphorus content in rhizosphere soil,and promote P absorption by P.hydropiper.Under the treatment of potassium dihydrogen phosphate,the effect of inoculating Kocuria sp.SLr15 on the growth and root morphology of P.hydropiper was better.