Responses of rice grain yield and quality to factorial combinations of ambient and elevated CO2 and temperature in T-FACE environments

The responses of rice (Oryza sativa L.) yield and quality to the combination of elevated CO2 and elevated temperature under open-air field conditions are still poorly understood. A japonica rice cultivar Wuyungeng 23 was grown under four combination of two levels of CO2 (ambient and enriched up to 590 μmol mol−1) and two levels of canopy temperature (ambient and warmed by 1.7–2.2 ºC during both night-time and day-time or during only day-time) in T-FACE (temperature by free-air CO2 enrichment) systems over two years. Our results showed that grain yield was decreased by 15.1% under the combination of elevated CO2 and elevated both night-time and day-time temperature, but increased by 3.5% under the combination of elevated CO2 and elevated only day-time temperature. Among yield components, panicle number, spikelet fertility and single grain weight significantly contributed to yield variations under the four CO2 and temperature treatments over two years. Interannual variations in these three yield components were associated with large interannual variations in air temperature after flowering and in solar radiation before flowering under ambient conditions. Among grain quality traits, chalky grain percentage and chalkiness degree also showed large interannual variations under the four CO2 and temperature treatments. Both chalky grain percentage and chalkiness degree increased with a decrease in grain yield under elevated CO2 and elevated temperature across years. Our study suggests that both grain yield and grain quality of rice need to be sustained under future climate change.