Abstract: 【OBJECTIVE】The interactive effects of light strength and nitrogen supply on soybean growth and photosynthetic physiology were studied. 【METHOD】Plant growth, photosynthetic gas exchange and chlorophyll fluorescence in soybean ( Glycine max (L.) cv. Heinong 37 ) were investigated after inoculated with Sinorhizobium fredii USDA191 under light-shaded and subsequent light-recovered conditions.【RESULTS】The results showed that, under non-shaded condition, plant biomass, chlorophyll contents and photosynthetic capacity were significantly increased in soybean following rhizobial inoculation as compared to those of the control plants; while under light-shaded condition, the photosynthetic rate of the rhizobia-inoculated soybean was markedly decreased compared to the non-inoculated control plants due to the influences of stomatal conductance and non-stomatal factors, showing that the inoculated rhizobia did not play the role in nitrogen fixation. Under light-recovered condition, the photosynthetic parameters were not recovered to the degree as that of the non-inoculated control plants. 【CONCLUSION】It is concluded that the positive effects of symbiotic nitrogen fixation can be attained only under suitable light condition.

Key words: soybean, shading, rhizobia, photosynthetic characteristics