Abstract:The leaves and cotyledons of aseptic soybean plants can emit and transform N2O under aerobic condition. But obvious differences of N2O emission rate were obsered under different nitrogen sources and light durations: The emission rate of N2O from nitrate-nitrogen culture was 15 % higher than that from ammonium-nitrogen and it was also three times higher in light for four hours than in light for eight hours. The results also showed that N20 can not be released from soybean leaves without acetylene during the incubation. If giving N2O to soybean leaves without acetylene, Authors found that little NzO released, infering that N20 was changed into another product in the leaves.