七十年代以来,作为生物固氮的一个分支——联合固氮的研究有较大进展。虽然定量地评价这种固氮作用尚不能满意做到,然而,它对土壤中氮素的增加无疑是有贡献的。目前已有许多关于水稻、小麦、玉米、甘蔗等作物联合固氮作用的报道。较多的报道认为这类固氮菌大多数在作物的近根区,也有一些认为可能进入植物根内。对于水稻联合固氮作用的研究,用最大有效数法测定水稻植株根表、根内异养固氮菌的数量,国外也曾有过报道,但尚缺乏从稻根组织内直接找到固氮菌的依据。为了探索这个问题,我们在对水 Since the seventies, as a branch of biological nitrogen fixation - joint nitrogen fixation has made great progress. Although quantitative evaluation of this nitrogen fixation is not yet satisfactory, however, it undoubtedly contributed to the increase of nitrogen in the soil. At present, there are many reports on the combined nitrogen fixation of crops such as rice, wheat, corn and sugar cane. More reports suggest that most of these Azotobacter species are near the root zone of the crop and some think it is possible to enter the plant root. For the study on the combined effect of nitrogen fixation in rice, the maximum effective number method was used to determine the number of heterotrophic azotobacter in the root and root of rice plants, which have been reported in foreign countries. However, there is still no basis for directly finding nitrogen-fixing bacteria in the rice root tissue. In order to explore this issue, we are on the water