The Micro-ecological Mechanism Of Phosphorus Utilization Of Cenchrus Spinifex

Cenchrus spinifex is an invasive weed that invades the agricultural and pasture areas of northern China.It can grow rapidly and expand population in the barren sandy soil with limited phosphorus,and form a single dominant community in a very short time.To analyze the positive feedback ecological response mechanism of C.spinifex under phosphorus stress from the perspective of soil phosphate solubilizing microorganisms and plant phosphatase,will have theoretical significance for revealing the invasion mechanism of C.spinifex and formulating scientific and effective prevention and control measures.In this study,C.spinifex occurred in large area in Horqin sandy grassland,with its associated plants Setaira viridis,Agropyron cristatum and control,were studied for indoor pot and hydroponic experiments.The community structure characteristics of phosphate solubilizing bacteria in rhizosphere soil of different treatments were analyzed by high-throughput 16S rRNA??sequencing and rep-PCR gene fingerprinting technology.The activity of endocrine phosphatase in plant leaves and roots was studied by using the kit extraction and spectrophotometry.The main results are as follows:1.The number of organic phosphobacteria and inorganic phosphobacteria of C.spinifex increased by 87.0% and 36.7%,respectively.The total amount of organic phosphorus bacteria was higher than that of S.viridis,A.cristatum and control(P < 0.05);the abundance and diversity of phosphate solubilizing bacteria community in rhizosphere soil of C.spinifex were significantly higher than that of control(P < 0.05),but significantly lower than that of S.viridis and A.cristatum(P < 0.05);the evenness index of phosphate solubilizing bacteria in the rhizosphere soil of C.spinifex was significantly higher than that of S.viridis,A.cristatum and control(P < 0.05);there was no common dominant community for phosphate solubilization in the four soils,the results showed that the inorganic phosphorus bacteria identified in the rhizosphere soil samples of C.spinifex belonged to Chryseobacterium.2.The results of OTU taxonomy and alpha diversity analysis showed that C.spinifex had the highest total number of OTUs,and the number of unique OTUs was also the highest compared with that of S.viridis and A.cristatum;Shannon index and Chao1 index of phosphate solubilizing bacteria in rhizosphere of C.spinifex were higher than those of S.viridis,A.cristatum and control;the results of PCA and UPGMA showed that the community composition of phosphate solubilizing bacteria in the rhizosphere soil of C.spinifex was highly similar with that of S.viridis.LEfSe analysis showed that five phosphate solubilizing bacteria groups in the rhizosphere soil of C.spinifex were significantly enriched and significantly different with others,which belonged to Alphaproteobacteria,Streptomyces_sp_ZFG47,Streptomycetales,Streptomycetaceae,and Streptomyces.Among them,?-Proteus and Streptomyces may play an important role in the invasion of C.spinifex.Redundancy analysis(RDA)showed that Actinomycetes were closely related to the content of available phosphorus in rhizosphere soil of C.spinifex.3.There was no significant difference in phosphorus content between C.spinifex,S.viridis and A.cristatum.Under normal culture(without stress),the acid phosphatase activity of the root system of C.spinifex was lower than that of S.viridis and A.cristatum.However,under phosphorus deficiency stress,the content of acid phosphatase secreted by roots of C.spinifex increased rapidly,and the release of acid phosphatase was significantly higher than that of associated plants.The results revealed the positive feedback regulation mechanism of C.spinifex in order to adapt to the poor habitat and enhance the competitiveness under nutrient stress.