ICG-3: Phytosphere, Forschungszentrum Jülich, D-52425 Jülich, Germany.
J Exp Bot. 2010 Feb;61(4):1031-9. doi: 10.1093/jxb/erp368. Epub 2009 Dec 15.
Leaves within a canopy are exposed to a spatially and temporally fluctuating light environment which may cause lateral gradients in leaf internal CO(2) concentration and diffusion between shaded and illuminated areas. In previous studies it was hypothesized that lateral CO(2) diffusion may support leaf photosynthesis, but the magnitude of this effect is still not well understood. In the present study homobaric leaves of Vicia faba or heterobaric leaves of Glycine max were illuminated with lightflecks of different sizes, mimicking sunflecks. Photosynthetic properties of the lightfleck areas were assessed with combined gas exchange measurements and chlorophyll fluorescence imaging. Lateral diffusion in homobaric leaves with an interconnected intercellular air space stimulated photosynthesis and the effect was largest in small lightfleck areas, in particular when plants were under drought stress. Such effects were not observed in the heterobaric leaves with strongly compartmented intercellular gas spaces. It is concluded that lateral diffusion may significantly contribute to photosynthesis of lightfleck areas of homobaric leaves depending on lightfleck size, lateral diffusivity, and stomatal conductance. Since homobaric leaf structures have been reported for many plant species, it is hypothesized that leaf homobary may have an impact on overall plant performance under conditions with a highly heterogeneous light environment.
叶冠内的叶片会暴露在时空波动的光照环境中，这可能导致叶片内部 CO2 浓度和遮荫与光照区域之间扩散的侧向梯度。在先前的研究中，有人假设侧向 CO2 扩散可以支持叶片光合作用，但这种效应的程度仍未被很好地理解。在本研究中，采用不同大小的光斑模拟光斑来照射蚕豆的等面叶或大豆的异面叶。用光斑区域的联合气体交换测量和叶绿素荧光成像来评估光合特性。具有连通细胞间空气空间的等面叶中的侧向扩散刺激了光合作用，并且在小光斑区域效果最大，特别是在植物受到干旱胁迫时。在具有强烈分隔细胞间气体空间的异面叶中没有观察到这种效应。因此得出结论，侧向扩散可能会根据光斑大小、侧向扩散率和气孔导度显著促进光斑区域的光合作用。由于许多植物物种都报告了等面叶结构，因此假设在高度异质的光照环境条件下，叶片等面性可能会对整体植物性能产生影响。
