In plants, stomata control water loss and CO₂ uptake. The aperture and density of stomatal pores, and hence the exchange of gases between the plant and the atmosphere, are controlled by internal factors such as the plant hormone abscisic acid (ABA) and external signals including light and CO₂. In this study, we examine the importance of ABA catabolism in the stomatal responses to CO₂ and light. By using the ABA 8′-hydroxylase-deficient Arabidopsis thaliana double mutant cyp707a1 cyp707a3, which is unable to break down and instead accumulates high levels of ABA, we reveal the importance of the control of ABA concentration in mediating stomatal responses to CO₂ and light. Intriguingly, our experiments suggest that endogenously produced ABA is unable to close stomata in the absence of CO₂. Furthermore, we show that when plants are grown in short day conditions ABA breakdown is required for the modulation of both elevated [CO₂]-induced stomatal closure and elevated [CO₂]-induced reductions in leaf stomatal density. ABA catabolism is also required for the stomatal density response to light intensity, and for the full range of light-induced stomatal opening, suggesting that ABA catabolism is critical for the integration of stomatal responses to a range of environmental stimuli.

在植物中，气孔控制水分流失和 CO ₂吸收。气孔的孔径和密度，以及因此植物与大气之间的气体交换，受植物激素脱落酸（ABA）等内部因素和光和CO ₂等外部信号的控制。在这项研究中，我们检查了 ABA 分解代谢在气孔对 CO ₂和光的反应中的重要性。通过使用 ABA 8'-羟化酶缺陷型拟南芥双突变体cyp707a1 cyp707a3，它不能分解而是积累高水平的 ABA，我们揭示了控制 ABA 浓度在介导气孔对 CO _{2反应中的重要性}和光。有趣的是，我们的实验表明，在没有 CO ₂的情况下，内源产生的 ABA 无法关闭气孔。此外，我们表明，当植物在短日照条件下生长时，ABA 分解是调节升高的 [CO ₂ ] 诱导的气孔关闭和升高的 [CO ₂ ] 诱导的叶气孔密度降低所必需的。ABA 分解代谢也是气孔密度对光强度的响应以及光诱导的气孔开放的全部范围所必需的，这表明 ABA 分解代谢对于气孔响应对一系列环境刺激的整合至关重要。