About this Research Topic
Plants respond to water and heat stress by adopting different strategies that may help them to survive and grow. Buffering the leaf water status by adjusting the width of stomatal opening to regulate the rate of passage of water vapour from the plant to the atmosphere is one of the several adaptive mechanisms to drought and heat. Elevated atmospheric CO2 concentration (e[CO2]) also reduces stomatal conductance (gs) through stomatal closure, but the mechanisms by which e[CO2] and soil water deficits induce stomatal closure can be different. When plants are grown under e[CO2], they display different strategies for regulating gs. One of them is through co-ordinated short-term physiological responses (change in aperture) and long-term morphological adjustments (change in stomatal density) to regulate water use efficiency. On the other hand, gs decreases in response to soil drying mainly due to partial stomatal closure induced by root-to-shoot chemical signaling (mainly xylem-borne abscisic acid, ABA) at moderate water stress and by the decrease in leaf turgor under severe water stress. The stomatal density can also be modified in response to prolonged soil water deficits. It is believed that water stress has a stronger impact on gs than e[CO2], and when plants are grown under combined water stress and e[CO2], the water deficits induce a reduction in gs that often offsets the reduction caused by e[CO2]. In addition, e[CO2] has a direct effect on attenuating the damage of water stress by reducing gs and transpiration rate. There are also indications that e[CO2] improves plant water status by reducing gs, while improving water use efficiency, but whether it occurs under well-watered or mild water stress conditions is unknown. In addition, water stress is often coupled with increases in ambient temperature, which tends to increase the root hydraulic conductivity, the transpiration rate, and gs.
Then the important questions to answer will be whether and how crop plants grown under e[CO2] can regulate stomatal behavior and water use when experiencing drought and heat stresses. The ability of crop plants to tolerate drought under the increasing concentrations of atmospheric [CO2] and temperature is largely dependent on the effectiveness of stomatal control over transpiration. The sensitivity of gs to ABA signaling during soil drying could be modified by e[CO2] and high temperature; yet to date, there is no consensus regarding the modulation of CO2growth environment on the response of gs to soil water deficits and heat stress. Also, it remains largely unknown about the significance of hydraulic and chemical signals in controlling gs of drought-stressed plants grown under e[CO2] and high temperatures. Therefore, there is a need to examine how e[CO2] modulates gs response to soil drying and heat stress in different crop species, and what are the underlying bio-physiological mechanisms regulating stomatal aperture of plants grown in a future warmer, drier and CO2-enriched climate.
This Research Topic aims to access and make available the state-of-the-art research progress on the interactive effects of e[CO2] x drought x high temperature on plant water relation characteristics. The Research Topic will focus on exploring the mechanisms regulating leaf gas exchange and water use efficiency across different crop species as influenced by drought and heat stress under CO2 elevation. The scale of the contributions will be at local, regional and global. We welcome authors to report original and novel research on the effect of drought and heat stress, individually or in combination, on stomatal aperture and morphology under a CO2-enriched environment. Modeling approaches will also be considered to simulate the response of gs in response to changes of these abiotic factors.
We encourage submission from various disciplines, as case studies, reviews and viewpoint papers. Descriptive studies that compile experimental data without providing a mechanistic insight into the described phenomena will not be considered for review.
Keywords: CO2 Elevation, Drought, Heat, Stomatal Conductance, Chemical Signalling
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