Abstract: To investigate the soybean nitrogen fixation ability response to the inoculation of different rhizobi⁃ um, two soybean varieties, Nandou 20 ( ND20 ) and Nanxiadou 25 (ND25), were inoculated with Bradyrhizobium ja⁃ ponicum 5038 and B. japonicum 5136 in this field experiment. The photosynthetic traits, chlorophyll content, nodule number and the physiological index of fresh nodule, such as sucrose content, leghaemoglobin content and nitroge⁃ nase reductive ability were investigated. The result revealed that chlorophyll content (chl), photosynthetic rate (Pn) and stomatal conductance (Gs) increased significantly but chla/b value decreased significantly after inoculation. Nodule number, nodule biomass, shoot and root biomass all increased significantly, biomass per nodule and root/ shoot value changed without significace. Sucrose content, leghemoglobin content and nitrogenase reductive ability of nodule all increased significantly. Compared with ND20, ND25 had bigger increasing amplitude, not only the photo⁃ synthetic characteristics but also the nodule characteristics and nitrogenase reductive ability.

Key words: color:#000000, font-family:", sans serif", ,tahoma,verdana,helvetica, font-size:12px, font-style:normal, font-weight:normal, line-height:1.5, text-decoration:none, "> , soybean；rhizobium；photosynthetic characteristics；nodule；nitrogen fixation ability ,