Institute of Technology, University of Tartu, Nooruse 1, Tartu 50411, Estonia.
Institute of Bioengineering, University of Tartu, Nooruse 1, Tartu 50411, Estonia.
Plant Physiol. 2024 Sep 2;196(1):608-620. doi: 10.1093/plphys/kiae320.
Stomatal pores that control plant CO2 uptake and water loss affect global carbon and water cycles. In the era of increasing atmospheric CO2 levels and vapor pressure deficit (VPD), it is essential to understand how these stimuli affect stomatal behavior. Whether stomatal responses to sub-ambient and above-ambient CO2 levels are governed by the same regulators and depend on VPD remains unknown. We studied stomatal conductance responses in Arabidopsis (Arabidopsis thaliana) stomatal signaling mutants under conditions where CO2 levels were either increased from sub-ambient to ambient (400 ppm) or from ambient to above-ambient levels under normal or elevated VPD. We found that guard cell signaling components involved in CO2-induced stomatal closure have different roles in the sub-ambient and above-ambient CO2 levels. The CO2-specific regulators prominently affected sub-ambient CO2 responses, whereas the lack of guard cell slow-type anion channel SLOW ANION CHANNEL-ASSOCIATED 1 (SLAC1) more strongly affected the speed of above-ambient CO2-induced stomatal closure. Elevated VPD caused lower stomatal conductance in all studied genotypes and CO2 transitions, as well as faster CO2-responsiveness in some studied genotypes and CO2 transitions. Our results highlight the importance of experimental setups in interpreting stomatal CO2-responsiveness, as stomatal movements under different CO2 concentration ranges are controlled by distinct mechanisms. Elevated CO2 and VPD responses may also interact. Hence, multi-factor treatments are needed to understand how plants integrate different environmental signals and translate them into stomatal responses.
控制植物 CO2 吸收和水分损失的气孔会影响全球碳和水循环。在大气 CO2 水平和蒸气压亏缺（VPD）不断增加的时代，了解这些刺激如何影响气孔行为至关重要。气孔对亚环境和超环境 CO2 水平的反应是否受相同的调节剂控制并取决于 VPD 尚不清楚。我们在拟南芥（Arabidopsis thaliana）气孔信号突变体中研究了气孔导度对 CO2 水平的响应，这些突变体中的 CO2 水平要么从亚环境升高到环境（400 ppm），要么在正常或升高的 VPD 下从环境升高到超环境水平。我们发现，参与 CO2 诱导气孔关闭的保卫细胞信号成分在亚环境和超环境 CO2 水平下具有不同的作用。CO2 特异性调节剂对亚环境 CO2 反应的影响更为显著，而缺乏保卫细胞慢型阴离子通道 SLOW ANION CHANNEL-ASSOCIATED 1（SLAC1）则更强烈地影响超环境 CO2 诱导的气孔关闭速度。在所有研究的基因型和 CO2 转变中，高 VPD 导致较低的气孔导度，以及在一些研究的基因型和 CO2 转变中，CO2 响应速度更快。我们的结果强调了实验设置在解释气孔 CO2 响应中的重要性，因为不同 CO2 浓度范围内的气孔运动由不同的机制控制。高 CO2 和 VPD 响应也可能相互作用。因此，需要进行多因素处理以了解植物如何整合不同的环境信号并将其转化为气孔响应。
