Summary Leaf architecture impacts the ease of gases diffusion, biochemical process, and photosynthetic performance. For balsam poplar, a widespread North American species, the influence of water availability on leaf anatomy and subsequent photosynthetic performance remains unknown. To address this shortcoming, we characterized the anatomical changes across the leaf profile in three‐dimensional space for saplings subjected to soil drying and rewatering using X‐ray microcomputed tomography. Our hypothesis was that higher abundance of bundle sheet extensions (BSE) minimizes drought‐induced changes in intercellular airspace volume relative to mesophyll volume (i.e. mesophyll porosity, θIAS) and aids recovery by supporting leaf structural integrity. Leaves of ‘Carnduff‐9’ with less abundant BSEs exhibited greater θIAS, higher spongy mesophyll surface area, reduced palisade mesophyll surface area, and less veins compared with ‘Gillam‐5’. Under drought conditions, Carnduff‐9 showed significant changes in θIAS across leaf profile while that was little for ‘Gillam‐5’. Under rewatered conditions, drought‐induced changes in θIAS were fully reversible in ‘Gillam‐5’ but not in ‘Carnduff‐9’. Our data suggest that a ‘robust’ leaf structure with higher abundance of BSEs, reduced θIAS, and relatively large mesophyll surface area provides for improved photosynthetic capacity under drought and supports recovery in leaf architecture after rewatering in balsam poplar.

中文翻译：

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绘制干旱诱导的香脂杨叶片剖面组织特征变化的图


总结 叶结构影响气体扩散的难易程度、生化过程和光合作用性能。对于广泛分布的北美物种香脂杨树，水分可用性对叶片解剖结构和随后的光合作用性能的影响仍然未知。为了解决这一缺点，我们使用 X 射线显微计算机断层扫描表征了经过土壤干燥和再浇水的树苗在三维空间中叶廓的解剖变化。我们的假设是，较高的束片延伸 （BSE） 丰度最大限度地减少了干旱引起的细胞间空容相对于叶肉体积的变化（即叶肉孔隙率，θIAS），并通过支持叶片结构完整性来帮助恢复。与 'Gillam-5' 相比，BSE 较少的 'Carnduff-9' 叶子表现出更大的 θIAS、更高的海绵状叶肉表面积、更小的栅栏叶肉表面积和更少的叶脉。在干旱条件下，Carnduff-9 在整个叶片轮廓上显示出 θIAS 的显著变化，而 'Gillam-5' 的变化很小。在再浇水条件下，干旱诱导的 θIAS 变化在 'Gillam-5' 中是完全可逆的，但在 'Carnduff-9' 中则不然。我们的数据表明，具有较高 BSE 丰度、降低 θIAS 和相对较大的叶肉表面积的“健壮”叶结构可在干旱下提高光合能力，并支持香脂杨树重新浇水后叶片结构的恢复。