Co-elevation of atmospheric CO2 and temperature affect instantaneous and intrinsic water use efficiency of rice varieties

Greenhouse gas (GHG) emissions from anthropogenic activities are the most significant drivers of climate change, which has both direct and indirect effects on crop production. The study was conducted during the kharif season for two years inside the Open Top Chamber (OTC) at the Genetic-H field of ICAR-Indian Agriculture Research Institute (IARI) to quantify the effect of elevated CO2 and temperature on water use efficiency of rice varieties. There were two different CO2 concentrations i.e. ambient (410 ppm) and elevated (550 ± 25 ppm) and also two different temperature levels i.e. ambient and elevated (+2.5-2.9°C). Results suggested that warming caused more accumulated GDD in rice and which negatively affected the duration of both the varieties. In elevated CO2 plus high temperature interaction treatment net photosynthesis rate was more than that of chamber control. Stomatal conductance and transpiration rate reduced with co-elevation of CO2 and temperature. Co-elevation of CO2 and temperature, has also improved WUE (both instantaneous and intrinsic) through enhanced carbon assimilation and reduced stomatal conductance, thus, reducing the amount of water lost through transpiration, eventually improving WUE of the crop.