The scenarios relevant to future climate change include not only elevated atmospheric CO₂ concentration (e[CO₂]), but also extreme climatic events, such as drought episodes.

The e[CO₂] and drought play central roles in affecting stomatal morphology, which directly affects the maintenance of crop water relationship and crop yield. Numerous studies have reported that e[CO₂] could alleviate the negative effects of drought stress on crops.

Recently, Prof. LI Xiangnan from Northeast Institute of Geography and Agroecology of the Chinese Academy of Sciences and Prof. LIU Fulai from University of Copenhagen in Denmark were invited to publish a review on crop response to the interaction of e[CO₂] and drought stress. The review was published in Current Opinion in Plant Biology.

The researchers systematically summarized the different mechanisms of e[CO₂] and drought in inducing stomata closure, and found abscisic acid (ABA) may be the common key player in these processes.

They proposed that higher water use efficiency under e[CO₂], which is mediated by ABA, could benefit the drought adaptation. The ABA loaded by xylem sap regulates stomata morphology and drought tolerance. The switch from ABA-limited to hydraulically limited stomatal aperture during drought stress provides plants with a better water management strategy.

However, e[CO₂] may affect this drought adaptation process by delaying the response of ABA-regulated stomata to drought. Therefore, the pros and cons of the e[CO₂]-modulated stomatal moving on plant drought adaptation may coexist.

All in all, the researchers elucidated how e[CO₂] modulates the stomatal response to drought stress. In addition, they believe it is necessary to further clarify the physiological process of e[CO₂] regulating stomata in response to multiple complex abiotic stresses, to provide a basis for improving crop water and fertilizer use efficiency under future climate conditions.