Estabishment mechanisms of Azospirillum associaitve nitrogen fixing bacteria on plant roots.

研究了固氮菌在植物根系上的定植机理。获得了以下结果。（1）细菌对植物根系的粘附能力因所用菌种或植物种类而有显著差异。细菌粘附可能是一个重要的过程中建立。然而，无法获得支持宿主特异性的直接证据。（2）玉米根上吸附细菌的生长特性表明，根上细菌数量的增加与吸附细胞的数量无关。细菌生长特性比细菌粘附性更重要。(3)We发现细菌之间的相互作用共同接种到玉米，如生长刺激或抑制。我们认为这种相互作用是细菌在玉米根上繁殖的重要机制。（4）固氮菌与非固氮菌的混合接种对固氮菌的固氮作用没有影响，但固氮菌的固氮作用受到结合态氮的抑制。(5)玉米根系分泌物中的碳水化合物约85%由糖和15%的有机酸组成。糖组分中以葡萄糖为主。（6）葡萄糖和乙醛酸具有引诱作用，但巴西相思不能同化。氮源抑制固氮菌的迁移。（7）测定了所用菌株对碳源的利用率。这表明，细菌之间的同化和竞争吸收的性质在建立机制中起着重要的作用。

We investigated mechanisms of how inoculated Azospirillum establishe theirself on plant roots. Following results were obtained.(1)Adhesion capability of bacteria to plant roots was markedly different in bacterial species or plant species used. Bacterial adhesion may be an important process in establishment. However,a direct evidence to support host specificity could not be obtained.(2)Growth characteristics of bacteria absorbed on maize roots showed that increase of bacterial numbers on roots was independent on numbers of adsorbed cells. Growth characteristics was more important factor than bacterial adhesion in estabishment mechanisms.(3)We found bacterial interactions between bacteria coinoculated to maize such as growth stimulation or inhibition. We assume that the interaction is very important mechanisms of the esteblishment ofbacteria on maizee roots.(4)Nitrogen fixation of Azospirillum was not influenced by the mixed inoculation with non-nitrogen fixing bacteria but repressed by combined nitrogen.(5) Carbohydrates in exudate from maize roots was composed of about 85% sugars and 15% organic acids. Glucose was dominantly contained in sugar fraction.(6)Glucose and glyoxylate were function as attractant,although A.brasilense could not assimilate them. Nitrogen source repressed mobility of Azospirillum.(7)Utilization of carbon sources was determined with strains used. It is suggested that the nature of assimilation of carbon surces and competition in uptake of carbon surces among bacteria play an important role in the mechanism of establishment.