Effects of elevated atmospheric ozone (pO₃) (50% higher than the ambient pO₃ in concentration) on root respiration and biomass accumulation and distribution of rice (Oryza sativa L. cv. Xiandao 63) at the jointing stage were investigated in fully open-air field conditions, and effect of alternation of anaerobic and aerobic conditions on root respiration was analyzed using special gas-collecting installations. Results show that under elevated pO₃ canopy and total biomass of the crop decreased slightly, while its root dry matter weight and ratio of root/canopy dropped significantly by 14.7% and 10.4%, respectively. The mixture of N₂ and O₂ at a ratio of 9:1 or 9.5:0.5 was the most propitious for root respiration, whereas in pure N₂, natural air and CO₂-saturated distilled water root respiration rate was lowered to a varying degree. The treatment of elevated pO₃ coupled with measurement inn CO₂-saturated distilled water and the treatment of ambient air coupled with measurement in pure N₂ was the least in root respiration rate, indicating that although the condition in which root respiration was measured affected root respiration rate, the impact was restricted in degree by the atmospheric environment in which the plant grew. The root respiration rate of rice growing under elevated ozone was 23.6%~52.7% higher than that under natural atmosphere when measured in pure gas condition, and the difference between the two was insignificant when the measurement was done in CO₂-saturated distilled water, showing that the influence of ozone pollution on root respiration obviously decreased. Under elevated and ambient pO₃ environments, root respiration of the rice displayed a curve of convex quadratic function with increasing oxygen supply in the gaseous environment for measurement. The oxygen concentration of 5%~10% in the environment promoted rice root respiration, while stronge anaerobic condition (i.e., pure N₂) and aerobic conditions (i.e., air) both affected root respiration of rice reversely.