What stops stomata reopening after a drought?
What stops stomata reopening after a drought?
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干旱后是什么阻止气孔重新打开？
DOI：
10.1093/treephys/tpad031
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发表时间：
2023
期刊：
影响因子：
4
通讯作者：
McAdam, Scott A
中科院分区：
文献类型：
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作者：
McAdam, Scott A
干旱是对陆地植物生命的生存威胁（Bro-dribb et al. 2020）。在低水势下，木质部栓塞切断土壤和叶片蒸发表面之间的液体连续体通常是致命的（Urli等人，2013年）。干旱可能是长期的、严重的和生态上不稳定的，随着气候的变化变得越来越常见（Choat等人，201 8），但到目前为止，最常见的干旱形式是间歇性的、非致命的缺水事件，在一个生长季节可能发生不止一次。气孔关闭是对任何干旱的第一生理反应之一，并且在阻止水势下降方面非常有效（Cochard等人，202 1）。对许多物种来说，干旱引起的气孔关闭在个体的一生中经常发生;在一些长寿的树木中，树木年轮记录表明干旱后气孔反复关闭的模式，以及多年来延迟的生长恢复（Anderegg等人，201 5）。鉴于干旱的反复发生，以及每一次干旱的潜在致命性，一个长期困扰植物生物学家的问题是：干旱是否会诱导水分保守的气孔功能（达尔文1898）？可以假设，如果连续发生频繁的干旱事件，或者水限制的打破是暂时的，那么保守的气孔从干旱中恢复（气孔不会像水势恢复一样快地重新打开至最大孔径）可能是有利的，因为限制了浪费即将稀缺的营养物质。类似的行为在发育过程中被视为对干旱的响应，在水分亏缺下开始的叶子具有较少的气孔（Yoo等人，20 - 10）。在这个问题上，Bi et al.（2022）探索了限制白蜡干旱后气体交换恢复的生理机制。Bi等（2022）报道，在从严重到足以关闭气孔的干旱中再浇水时，叶气体交换的完全恢复需要> 7天，而水势在再浇水的12小时内恢复。Bi等（2022）探索了两种可以解释干旱后气孔恢复延迟的假设，因为干旱期间的水势没有下降到诱导栓塞的水平，所以排除了木质部水力传导率降低的假设（Brodribb和Cochard 2009）。测试的第一个理论是植物激素脱落酸（阿坝）的水平，其对于种子植物在干旱期间关闭气孔至关重要（Mittelheuser和货车Steveninck 1969，Raschke 1975），在从干旱恢复之后保持高水平并逐渐下降。Bi等（2022）发现情况并非如此，就像叶水势迅速恢复一样，阿坝水平在复水后迅速下降。这留下了一个最终的假设，即另一个代谢信号是在干旱恢复时保持气孔关闭。Bi等（2022）发现，在F.这是气体，果实成熟激素乙烯。Bi等（2022）提供了一系列令人信服的实验，包括用乙烯拮抗剂处理的植物中的气体交换，以测量乙烯排放速率，以证明乙烯保持F.中国从干旱中恢复过来。Bi等（2022）得出结论，在间歇性和非致死性干旱后，乙烯作为气孔的保守用水信号（图1）。
Drought is an existential threat to terrestrial plant life (Bro-dribb et al. 2020). The severing of the liquid continuum between the soil and the evaporating surfaces of the leaf by xylem embolism at low water potentials is often lethal (Urli et al. 2013). Droughts can be long, severe and ecologically destabilizing, as is becoming increasingly common with changing climates (Choat et al. 201 8), but by far the most common form of drought is the intermittent, non-lethal episode of water deficit that can occur more than once in a growing season. Stomatal closure is one of the first physiological responses to any drought, and is very effective at arresting water potential decline (Cochard et al. 202 1). For many species, droughtinduced stomatal closure is a frequent occurrence over the life of an individual; in some long-lived trees, the tree-ring record suggests a pattern of repeated stomatal closure following drought, and delayed growth recovery for many years (Anderegg et al. 201 5). Given the repeated occurrence of droughts, and the potential lethality of each drought, a question that has long entertained plant biologists is: does a drought induce water-conservative stomata function (Darwin 1898)? It could be hypothesized that a conservative stomatal recovery from drought (stomata not reopening to maximum apertures as fast as water potentials recover) might be advantageous if there are frequent drought events in quick succession, or the break in water limitation is temporary, by limiting the waste of a soon-tobe scarce nutrient. A similar behavior is seen developmentally in response to drought, with leaves initiated under water deficit having fewer stomata (Yoo et al. 20 10). In this issue, Bi et al.(2022) explores the physiological mechanism restricting gas exchange recovery following drought in Fraxinus chinensis. Bi et al.(2022) report that on rewatering from a drought severe enough to close stomata, the complete recovery of leaf gas exchange took> 7 days, yet water potentials recovered within 12 h of rewatering. Bi et al.(2022) explored two hypotheses that could explain this delayed stomatal recovery following drought, given that reduced xylem hydraulic conductivity (Brodribb and Cochard 2009) was ruled out because water potentials during drought did not drop to a level that would induce embolism. The first theory tested was that the levels of the phytohormone abscisic acid (ABA), which is critical for closing stomata during drought in seed plants (Mittelheuser and Van Steveninck 1969, Raschke 1975), remained high following recovery from drought and gradually declined. Bi et al.(2022) found that this was not the case and that like leaf water potential, which rapidly recovered, ABA levels declined rapidly on rewatering. This left a final hypothesis that another metabolic signal was keeping stomata closed on recovery from drought. Bi et al.(2022) found that in F. chinensis this was the gaseous, fruit-ripening hormone ethylene. Bi et al.(2022) provide a compelling series of experiments, including gas exchange in plants treated with ethylene antagonists, to measuring ethylene emission rates, to demonstrate that ethylene keeps the stomata of F. chinensis closed on recovery from drought. Bi et al.(2022) conclude that ethylene acts as a conservative water-use signal for stomata following an intermittent and non-lethal drought (Figure 1).