Elevated CO2 alleviates the exacerbation of evapotranspiration rates of grapevine (Vitis vinifera) under elevated temperature

Climate change is increasing crop water consumption while reducing precipitations in most places where grapevines are grown. This study aimed to quantify whole-plant water consumption of grapevines under climate change factors to determine what are the biggest contributors to changes in evapotranspiration under climate change conditions. Two experiments were carried out: i) Cabernet Sauvignon grafted onto 110 R grown in the temperature gradient greenhouses (TGG) exposed to elevated CO2 (700 µmol mol−1) and/or elevated temperature (+4 °C) and ii) Tempranillo vegetative cuttings grown in the controlled environment greenhouses (CEG) exposed to ambient CO2 and standard temperatures (i.e CA24°C) or elevated CO2 combined with elevated temperature (i.e CE28°C) under cyclic water deficit conditions. In the overall, the combination of elevated CO2 and elevated temperature did not increase pot evapotranspiration, and in the only case this happened, it was mediated by a greater leaf area per plant. There was an interaction in which CO2 compensated for the increase in evapotranspiration induced by elevated temperature. Plants under elevated CO2 and elevated temperature (CETE) had lower stomatal conductance which resulted in similar transpiration rates to plants under ambient CO2 and ambient temperature conditions (CATA) despites the 4 °C increase. Net assimilation was greater under elevated CO2, and thus, instantaneous water use efficiency (WUE). Pot evapotranspiration was correlated to parameters such as leaf area per plant, gas exchange transpiration rates, reference evapotranspiration and plant available water content in the substrate. Pot lysimeters are a good compromise to study whole-plant water consumption rates under controlled conditions. Climate change conditions will likely continue to threat the sustainability of crops due to water shortages, however, our results point out that the interaction between elevated temperature and CO2 should be considered. The sensitivity of plant responses to elevated CO2 could be exploited as a key trait for the adaptation of crops to climate change.