Response of WUE of maize at ear stage to the coupling effect of CO and temperature.

In the face of global warming, the photosynthesis and transpiration of plants will change greatly, which will ultimately affect the water use efficiency (WUE) of plants. In order to study the coupling effects of CO and temperature on WUE of maize at ear stage, 'Zhengdan 958' was taken as the research object, and 5 temperatures (20 °C, 25 °C, 30 °C, 35 °C and 40 °C) and 11 CO concentration (400, 300, 200, 150, 100, 50, 400, 400, 600, 800 and 1000 μmol mol) were set to measure the parameters such as net photosynthetic rate (), transpiration rate (), stomatal conductance () and intercellular CO concentration () of single leaves. The response of WUE (/) to CO and temperature was evaluated by a CO response model. The results show that at the same temperature, and WUE increased with CO level, while decreased as CO level increases; at the same CO concentration, and were both positively correlated with temperature, while WUE decreased with the increase of temperature. The maximum value of WUE was obtained when the CO concentration was 1000 μmol mol and the temperature was 20.0 °C. The results suggest that global warming will not improve WUE of maize, which will bring more severe challenges to water-saving agriculture and food security.