Plants can change leaf forms, adjusting light conditions on their adaxial and abaxial surfaces, to adapt to light environments and enhance their light use efficiencies. The difference between photosynthesis on the two leaf sides (dorsoventral asymmetry) is an important factor that affects light use efficiency. However, photosynthetic dorsoventral asymmetry is rarely compared under direct and diffuse light conditions. To estimate the impacts of recently reported alterations in direct and diffuse light in the sky radiation on plant carbon assimilation, variations in morphology between the two leaf sides in tobacco (Nicotiana tabacum L.) were investigated, and the dorsoventral responses of photosynthesis to illuminating directions were compared in direct and diffuse light. Dorsoventral asymmetry was reflected in stomatal densities, anatomic structures, and photochemical traits, which caused markedly different photosynthetic rates as well as stomatal conductances both in direct and diffuse light. However, the degree of photosynthetic asymmetry was weakened in diffuse light. The diffuse light caused a greater stomatal conductance on the abaxial side than direct light, which resulted in reduced photosynthetic asymmetry. In addition, the photosynthetic dorsoventral asymmetry could be affected by the photosynthetic photon flux density. These results contribute to understanding the dorsoventral regulation of photosynthesis in bifacial leaves, and provide a reference for breeding to cope with the increase in the proportion of diffuse light in the future.

中文翻译：

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烟草叶片的背腹光合不对称性响应于直接和漫射光。

植物可以改变叶片的形状，调节其正面和背面的光照条件，以适应光照环境并提高其光照利用效率。叶片两侧的光合作用之间的差异（背腹不对称）是影响光利用效率的重要因素。但是，很少在直射光和漫射光条件下比较光合背腹的不对称性。为了估计最近报道的天空辐射中直射光和漫射光的变化对植物碳同化的影响，研究了烟草（Nicotiana tabacum L.）的两个叶片侧面之间形态的变化，以及光合作用对发光方向的背腹响应在直接和漫射光下进行了比较。腹背不对称反映在气孔密度，解剖结构和光化学特性，在直射光和漫射光中引起明显不同的光合速率以及气孔导度。但是，在漫射光中光合不对称的程度减弱了。与直接光相比，漫射光在背面产生更大的气孔导度，从而降低了光合作用的不对称性。另外，光合背腹不对称性可能受光合光子通量密度的影响。这些结果有助于了解双面叶片光合作用的背腹调节，并为将来应对漫射光比例的增加提供参考。在直射光和漫射光下，它们的光合速率以及气孔导度都明显不同。但是，在漫射光中光合不对称的程度减弱了。与直接光相比，漫射光在背面产生更大的气孔导度，从而降低了光合作用的不对称性。另外，光合背腹不对称性可能受光合光子通量密度的影响。这些结果有助于了解双面叶片光合作用的背腹调节，并为将来应对漫射光比例的增加提供参考。在直射光和漫射光下，它们的光合速率以及气孔导度都明显不同。但是，在漫射光中光合不对称的程度减弱了。与直接光相比，漫射光在背面产生更大的气孔导度，从而降低了光合作用的不对称性。另外，光合背腹不对称性可能受光合光子通量密度的影响。这些结果有助于了解双面叶片光合作用的背腹调节，并为将来应对漫射光比例的增加提供参考。与直接光相比，漫射光在背面产生更大的气孔导度，从而降低了光合作用的不对称性。此外，光合背腹不对称性可能受光合光子通量密度的影响。这些结果有助于了解双面叶片光合作用的背腹调节，并为将来应对漫射光比例的增加提供参考。与直接光相比，漫射光在背面产生更大的气孔导度，从而降低了光合作用的不对称性。另外，光合背腹不对称性可能受光合光子通量密度的影响。这些结果有助于了解双面叶片光合作用的背腹调节，并为将来应对漫射光比例的增加提供参考。