几种水稻根际固氮菌与水稻联合共生固氮的研究

从水稻根际分离的两株固氮菌:肺炎克雷从伯氏菌(Klebsilla Pneumoniae)K—12,肠杆菌属(En—terobacter sp)E—25以及从国外引进的水稻根际固氮螺菌(Azospirill-um lipoferum FS),克雷伯氏菌(Klebsiella oxytoca NG13)菌株,分别接种于有水稻幼苗生长的无碳、无氮培养基中,于28℃暗培养条件下进行培养.以上各菌均能正常生长,并与水稻幼苗有联合固氮作用.其固氮活性分别如下:Azospirillum lipoferum FS菌株为10.5毫微克分子C_2H_4/株/小时,Klebsiella oxytoca NG13菌株为3.9毫微克分子,C_2H_4/株/小时,Klebsiella pneumoniae K—12菌株为4.9毫微克分子C_2H_4/株/小时,Enterobacter SP E—25菌株为2.9毫微克分子C_2H_4/株/小时.固氮菌与水稻联合共生于半固体培养基中时,菌在水稻胚乳周围生长旺盛、繁殖快、并形成菌环.用对DNA专一的荧光染料DAPI染色观察,以及扫描电镜观察均表明:这四种固氮菌均聚集并附着在水稻根表,大部分在根毛区.水稻根横切面的扫描电镜观察,以及对接种的水稻根内生菌的重新分离实验表明,部分固氮菌能够进入水稻根组织的皮层薄壁细胞内生长并繁殖.

STUDIES ON THE ASSOCIATIVE SYMBIOTIC NITROGEN FIXATION OF RICE SEEDLING INOCULATED WITH SOME NITROGEN FIXING BACTERIA ISOLATED FROM THE RHIZOSPHERE OF RICE

TWO strains of nifogen fixing bacteria, Klebsiella pneumoniae K-12 and Enterobscter sp. E-25, isolated from the rhizosphere of local paddy fields were examined for their associative nitrogen fixation with rice seedlings cultured on C and N free media, in comparison with two known strains Azos-Pirillum lipoferum FS and Klebsiella oxytaca NG-13 introduced from abroad. All of the above strains could grow and possess associative nitrogen fixation activity under dark incubation conditions at 28?. The nitrogen fixing activities of these associations were as follows. 10.5 nmol C2H4/seedling/hr. for Azospirillum Hpoferum FS,4.9 nmol C2H4/seedling/hr.for Klebsiella pneumon-iae K-12, 3.9 nmol C2H4/seedling/hr. for Klebsiella oxytoca NG-13, and 2.9 nmol C2H4/seedling/hr. for Enterobacter sp. E-25 respectively. With the exception of the aerobic Azospirillvm lipofervm FS, the other 3 strains grew vigerously around the endosperm of the seedling and formed a bacteria ring. By using DNA specific flourescenCe dye DAPI staining and scanning electron microscopic observations revealed that these 4 strains of the nitrogen fixing bacteria adhered to the root surface and built up a dense Population, Particularly at the root hair region. Scanning electron microscopic observation of the transverse section of the root and the re-isolation experiments of the endophytes indicated that the bacteria could invade the Parenchyma of the root cortex and propagate within the cell.