Activity and span of nitrogen fixation (acetylene reduction) of rhizobia in the symbiotic rhizobium-callus tissues changed by the carbon sources and concentrations. Hexoses were better than pentoses, and sugars were better than those organic acids, except the fumaric acid, for the rhizobial acetylene reduction in the symbiotic tissues. High concentration of sugar promoted the symbiotic tissues to senescence. No leghemoglobin was found in the symbiotic tissues. The lignification of callus tissues might have a regulatory function to prevent the nitro-genase in rhizobia of callus tissues from oxygen-denaturation. Negligible amount of N20 realeased by symbiotic system. The nitrate respiration might not provide energy to support the rhizobial acetylene reduction in symbiotic callus tissues.