中文摘要：

本研究以东祁连山高寒草地常见的7种禾本科牧草为材料,通过分离培养的方法研究了其根际细菌的数量和分布,重点研究了其有固氮作用的细菌数量和分布。结果发现,7种植物根际均存在大量的细菌,总数在2.50×10^6~17.07×10^6 cfu/g,不同植物根际细菌的数量和分布不同,以高原早熟禾根际细菌数量最多,冰草和赖草根际细菌最少,其余禾草居中;根际固氮菌的数量和分布也因牧草种类不同而不同。7种供试植物根际分离到固氮菌201株。且细菌和PGPR菌株的数量均呈现＂根系表面（RP）〉根际土壤（RS）〉根内（HP）＂的分布趋势,表现出强烈的根际效应。

英文摘要：

This research studied the quantity and distribution of bacteria in the rhizosphere of seven Poaceous species from the east Chi-lien Mountains.The research employed a cultivation method,and mainly studied nitrogen fixing bacteria.It was found that there were large numbers of bacteria in rhizospheres of all 7plant species studied.The total number of rhizosphere bacteria counted ranged from 2.5×10^6 cfu/g to 17.07×10^6 cfu/g,with Agropyron cristatumand Leymus secalinus having the lowest rhizosphere nitrogen-fixing bacterial populations and Poa alpigena having the highest,with the other 4species intermediate.A total of 201 nitrogenfixing strains were isolated from the 7grass species studied.The quantity of bacteria and PGPR present a distribution trend：＂root system surface（RP）〉root surface soil（RS）〉histoplan or interior of roots（HP）＂.