Abstract: The effect of boron deficiency, light intensity, supply with exogenous glucose and their interactions on nitrogenase activity of nodules in soybean plants were studied in nutrient solution under controlled condition. The absence of boron in the culture medium resulted in an inhibition of nitrogenase activity. Lower intensity in boron free medium didn't decrease nitrogenase activity. but supplying with glucose could not prevent the decrease of nitrogenase activity, in spite of increase of sucrose content in nodules after exogenous glucose. These results indicate that the decrease of nitrogenase activity of nodules under the boron-deficiency stress was not due to carbohydratedeficiency.