Abstract: | The continuing increase in atmospheric carbon dioxide concentration(CO2]) and projections of possible future increases in globalairtemperatures have stimulated interest in the effects of theseclimate variables on agriculturally important food crops. Thisstudywas conducted to determine the effects of CO2] and temperatureon rice (Oryza sativa L., cv. IR30). Rice plants weregrownseason-long in outdoor, naturally sunlit, controlled-environment,plant growth chambers in temperature regimes ranging from 25/18/21°Cto 37/30/34°C (daytime dry bulb air temperature/night-timedry bulb air temperature/paddy water temperature)and CO2] of660 µmol CO2 mol1 air. An ambient chamber was maintainedat a CO2] of 330 µmol mol1 and temperature regimesof 28/21/25°C. Carbon dioxide enrichment at 28/21/25°Cincreased both biomass accumulation and tillering and increasedgrain yield by 60%. In the 660 µmol mol1 CO2]treatment, grain yield decreased from 10.4 to 1.0 Mg ha1with increasing temperature from 28/21/25°C to the 37/30/34°Ctemperature treatment. Across this temperature range, the numberof panicles plant1 nearly doubled while the number ofseeds panicle1 declined sharply. These results indicatethat while future increases in atmospheric CO2] are likelyto be beneficial to rice growth and yield, potentially largenegative effects on rice yield are possible if air temperaturesalso rise. Key words: Oryza sativa, CO2, temperature, growth, yield |