Enhanced photosynthesis, transpiration regulation, water use-efficiency and growth in buckwheat outperforms wheat response to high [CO2], high temperature and drought

The rising atmospheric [CO 2 ] levels will increase global temperature and drought events, threatening wheat ( Triticum aestivum ) production. In recent years, buckwheat ( Fagopyrum esculentum ) has emerged as an alternative crop to wheat under extreme drought. However, it is essential to understand the ability of these species to withstand future climatic conditions where drought and high temperature will occur simultaneously in a high [CO 2 ] environment. Since the mitigating effect of high [CO 2 ] is strongly influenced by the severity of the stress, we compared the response of wheat and buckwheat, differently sensitive to drought, to future climatic scenarios. In wheat, high temperature and high [CO 2 ] passively decreased water potential, as shown by the higher dehydration. Likewise, future drought extremely increased water requirements, causing extreme reductions in the photosynthetic rate and in the quantum yield of PSII, as well as changes in the antioxidant metabolism. Conversely, buckwheat maintained optimal hydration levels, promoted higher photosynthetic rates and increased water -use efficiency under the combination of high [CO 2 ] and high temperature, with and without drought. The improved response of buckwheat was attributed to an enhanced stomatal regulation and water -use efficiency, and resulted in an outperforming growth under future climatic conditions compared to the growth in wheat. Our research highlights the promising potential of buckwheat as an alternative crop to wheat under future climatic scenarios.