Shope Joseph C, Peak David, Mott Keith A
Biology Department, Utah State University, Logan, UT 84322-5305, USA.
Plant Cell Environ. 2008 Sep;31(9):1290-8. doi: 10.1111/j.1365-3040.2008.01844.x. Epub 2008 Jun 6.
The ability of guard cells to hydrate and dehydrate from the surrounding air was investigated using isolated epidermes of Tradescantia pallida and Vicia faba. Stomata were found to respond to the water vapour pressure on the outside and inside of the epidermis, but the response was more sensitive to the inside vapour pressure, and occurred in the presence or absence of living, turgid epidermal cells. Experiments using helium-oxygen air showed that guard cells hydrated and dehydrated entirely from water vapour, suggesting that there was no significant transfer of water from the epidermal tissue to the guard cells. The stomatal aperture achieved at any given vapour pressure was shown to be consistent with water potential equilibrium between the guard cells and the air near the bottom of the stomatal pore, and water vapour exchange through the external cuticle appeared to be unimportant for the responses. Although stomatal responses to humidity in isolated epidermes are the result of water potential equilibrium between the guard cells and the air near the bottom of the stomatal pore, stomatal responses to humidity in leaves are unlikely to be the result of a similar equilibrium.
利用紫露草和蚕豆的离体表皮，研究了保卫细胞从周围空气中吸水和失水的能力。发现气孔对表皮内外的水汽压力有反应，但对内部蒸汽压力的反应更敏感，且无论有无活的、膨胀的表皮细胞都能发生这种反应。使用氦氧空气进行的实验表明，保卫细胞完全通过水蒸气进行吸水和失水，这表明没有明显的水分从表皮组织转移到保卫细胞。在任何给定蒸汽压力下达到的气孔孔径与保卫细胞和气孔孔底部附近空气之间的水势平衡一致，并且通过外部角质层的水汽交换似乎对这些反应并不重要。尽管离体表皮中气孔对湿度的反应是保卫细胞与气孔孔底部附近空气之间水势平衡的结果，但叶片中气孔对湿度的反应不太可能是类似平衡的结果。
