Effects of elevated ozone, carbon dioxide, and the combination of both on the grain quality of Chinese hybrid rice

The effects of CO2 and/or O3 elevation on rice grain quality were investigated in chamber experiments with gas fumigation performed from transplanting until maturity in 2011 and 2012. Compared with the control (current CO2 and O3 concentration), elevated CO2 caused a tendency of an increase in grain chalkiness and a decrease in mineral nutrient concentrations. In contrast, elevated O3 significantly increased grain chalkiness and the concentrations of essential nutrients, while changes in starch pasting properties indicated a trend of deterioration in the cooking and eating quality. In the combination of elevated CO2 and O3 treatment, only chalkiness degree was significantly affected. It is concluded that the O3 concentration projected for the coming few decades will have more substantial effects on grain quality of Chinese hybrid rice than the projected high CO2 concentration alone, and the combination of two gases caused fewer significant changes in grain quality than individual gas treatments.