Barratt Georgina E, Sparkes Debbie L, McAusland Lorna, Murchie Erik H
School of Biosciences, University of Nottingham, Loughborough, UK.
AoB Plants. 2020 Dec 2;13(1):plaa067. doi: 10.1093/aobpla/plaa067. eCollection 2021 Feb.
Under conditions of high transpiration and low soil water availability, the demand for water can exceed supply causing a reduction in water potential and a loss of cell turgor (wilting). Regulation of stomatal aperture mediates the loss of water vapour ( ), which in turn is dependent in part on the anatomical characteristics of stomatal density (SD) and stomatal size (SS). Anisohydric sugar beet () is atypical, exhibiting wilting under high soil water availability. Spinach () belongs to the same family ., but demonstrates a more typical wilting response. To investigate the role of stomatal dynamics in such behaviours, sugar beet and spinach leaves were exposed to step-changes in photosynthetic photon flux density (PPFD) from 250 to 2500 µmol m s. Using a four log-logistic function, the maximum rate of stomatal opening was estimated. Concurrent measurements of SD and SS were taken for both species. While sugar beet coupled faster opening with smaller, more numerous stomata, spinach showed the converse. After exposure to drought, maximum was reduced in sugar beet but still achieved a similar speed of opening. It is concluded that sugar beet stomata respond rapidly to changes in PPFD with a high rate and magnitude of opening under both non-droughted and droughted conditions. Such a response may contribute to wilting, even under high soil water availability, but enables photosynthesis to be better coupled with increasing PPFD.
在高蒸腾速率和土壤水分可利用性低的条件下，对水分的需求可能超过供应，导致水势降低和细胞膨压丧失（萎蔫）。气孔孔径的调节介导了水汽的散失（ ），而这又部分取决于气孔密度（SD）和气孔大小（SS）的解剖学特征。非等水线甜菜（ ）是个例外，在土壤水分可利用性高的情况下也会出现萎蔫。菠菜（ ）属于同一科（ ），但表现出更典型的萎蔫反应。为了研究气孔动态在这些行为中的作用，将甜菜和菠菜叶片暴露于光合光子通量密度（PPFD）从250到2500 μmol m⁻² s⁻¹的阶跃变化中。使用四参数对数逻辑斯蒂函数估计气孔最大开放速率。同时对两个物种的气孔密度和气孔大小进行了测量。虽然甜菜将更快的开放与更小、更多的气孔联系在一起，但菠菜则相反。干旱处理后，甜菜的最大（ ）降低，但仍达到了相似的开放速度。得出的结论是，甜菜气孔在非干旱和干旱条件下都对PPFD的变化做出快速响应，开放速率和幅度都很高。这种响应可能导致萎蔫，即使在土壤水分可利用性高的情况下也是如此，但能使光合作用更好地与增加的PPFD相耦合。
