<正>从 3个不同地点的 2 1个杨树无性系及半同胞家系根系和根际的不同部位分离到 1 5 1个菌株具有固氮酶活性 ,其中固氮酶活性高于 1 0 0nmol/(瓶·h) (还原乙炔的量 )的菌株有 8个。杨树不同无性系及半同胞家系根际固氮细菌的数量、种类及分布情况有差异。对固氮活性最高的 5个菌株 ( 1 2 5、3、71、74和 1 34号 )进行了初步鉴定 ,3号和 71号菌株均属贝杰林克菌属 (Beijerinckia) ,74号菌株属德克斯氏菌属 (Derxia) ,1 2 5号和 1 34号菌株的分类地位待定。杨树根际分离到的固氮细菌与禾本科植物根系分离的一些联合固氮细菌类群基本一致

One hundred and fifty one nitrogen fixing strains were isolated from twenty one Poplar clones and half families root systems and rhizospheres in different sites. Eight strains, nitrogenase activities were higher than 100(nmol C 2H 4/bottle·h). Different Poplar clones and half families rhizospheric nitrogen fixing bacteria, quantity、speciese and distribution were different. Five strains(No.125、3、71、74、134) with the highest nitrogenase activity were tentatively identified, No.3 and 71 strain both belong to Beijerinckia ,No.74 strain belongs to Derxia . The taxonomic position of No.125 and 134 strains remained unidentified. These strains isolated from Poplar rhizosphere are essentially identical with some nitrogen fixing bacteria at grasses and grain crops root systems.