The mechanical diversity of stomata and its significance in gas-exchange control
The mechanical diversity of stomata and its significance in gas-exchange control
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DOI：
10.1104/pp.106.089367
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发表时间：
2007-01-01
期刊：
影响因子：
7.4
通讯作者：
Farquhar, Graham D.
中科院分区：
文献类型：
--
作者：
Franks, Peter J.;Farquhar, Graham D.
鉴于气孔运动最终是一个机械过程，且气孔具有形态和机械多样性，我们探讨了气孔机械多样性对叶片气体交换的影响，并考虑了一些限制因素。对四种具有不同气孔形态的保护细胞进行了力学测量，包括三种典型的“肾”型和一种“哑铃”型；这些信息与气体交换测量数据一起用于模拟和比较各自的操作特性。基于在充足阳光和高湿条件下采集的叶片冷冻切片的扫描电镜图像，以及在最大和零表皮膨胀时气孔孔径与保护细胞膨胀关系的压力探针测量的证据，由此得出结论，在至少一种植物（禾草Triticum aestivum）中，如果不大幅降低气孔打开过程中辅助细胞的渗透压力（因此膨胀），以克服辅助细胞的巨大机械优势，就不可能获得最大气孔开度（和最大叶片扩散导度）。提出了一种机制，其必然结果是大大加快了气孔的打开和关闭。气交换测量结果表明，柽柽树具有非常快速的气孔运动能力，这可能是由于其哑铃形气孔的独特形态和力学特征，以及在气孔打开或关闭过程中保护细胞和辅助细胞之间的渗透和膨胀压力的“跷跷板”。这些特性可能是草类成功的基础。
Given that stomatal movement is ultimately a mechanical process and that stomata are morphologically and mechanically diverse, we explored the influence of stomatal mechanical diversity on leaf gas exchange and considered some of the constraints. Mechanical measurements were conducted on the guard cells of four different species exhibiting different stomatal morphologies, including three variants on the classical "kidney'' form and one "dumb-bell'' type; this information, together with gas-exchange measurements, was used to model and compare their respective operational characteristics. Based on evidence from scanning electron microscope images of cryo-sectioned leaves that were sampled under full sun and high humidity and from pressure probe measurements of the stomatal aperture versus guard cell turgor relationship at maximum and zero epidermal turgor, it was concluded that maximum stomatal apertures (and maximum leaf diffusive conductance) could not be obtained in at least one of the species (the grass Triticum aestivum) without a substantial reduction in subsidiary cell osmotic (and hence turgor) pressure during stomatal opening to overcome the large mechanical advantage of subsidiary cells. A mechanism for this is proposed, with a corollary being greatly accelerated stomatal opening and closure. Gas-exchange measurements on T. aestivum revealed the capability of very rapid stomatal movements, which may be explained by the unique morphology and mechanics of its dumb-bell-shaped stomata coupled with "see-sawing'' of osmotic and turgor pressure between guard and subsidiary cells during stomatal opening or closure. Such properties might underlie the success of grasses.