The movement of air to the rhizosphere through the plant tissue of lowland rice was studied using a15N-tracer technique. Rice plants, grown under submerged soil conditions, at different growth stages were placed in a glass chamber where the atmosphere of the shoot and root compartments was separated, permitting the shoot compartment to be filled with15N-labeled nitrogen gas. The atmosphere in the root compartment was analyzed for15N-labeled nitrogen periodically after the plants had been transferred to a greenhouse or growth chamber. Nitrogen gas taken up by the aerial plant parts moved to the roots and diffused into the rhizosphere. At the tillering stage, atmospheric nitrogen appeared to move slowly through plant tissues. The rate of movement of the atmospheric nitrogen was much greater in the rice plant at the heading or flowering stage than at tillering.