Mangifera indica is the fifth most consumed fruit worldwide, and the most important in tropical regions, but its anatomy is quite unexplored. Previous studies examined the effect of chemicals on the xylem structure in the stems of mango, but the anatomy of the phloem has remained elusive, leaving the long-distance transport of photoassimilates understudied. In this work, we used a combination of fluorescence and electron microscopy to evaluate in detail the structure of the sieve tube elements composing the phloem tissue in the tapering branches of mango trees. We then used this information to better understand the hydraulic conductivity of the sieve tubes following current models of fluid transport in trees. Our results revealed that the anatomy of the phloem in the stems changes from current year branches, where it was protected by pericyclic fibers, to older ones, where the lack of fibers was concomitant with laticiferous canals embedded in the phloem tissue. Callose was present in the sieve plates, but also in the walls of the phloem conduits, making them discernible from other phloem cells in fresh sections. A scaling geometry of the sieve tube elements, including the number of sieve areas and the pore size across tapering branches resulted in an exponential conductivity from current year branches to the base of the tree. Our measurements of the phloem in mango fit with measurements of the phloem architecture in the stems of forest woody species and imply that, despite agronomic pruning practices, the sieve conduits of the phloem scale with the tapering branches. As a result, the pipe model theory applied to the continuous tubing system of the phloem appears as a good approach to understanding the long-distance hydraulic transport of photoassimilates in fruit trees.

中文翻译：

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芒果中韧皮部的电导率

芒果（Mangifera indica）是世界上食用量第五大的水果，在热带地区也是最重要的水果，但是其解剖学尚未得到充分的开发。先前的研究检查了化学物质对芒果茎木质部结构的影响，但是韧皮部的解剖结构仍然难以捉摸，因此对光同化物的长距离运输尚缺乏研究。在这项工作中，我们使用了荧光显微镜和电子显微镜的组合来详细评估构成芒果锥状分支中韧皮部组织的筛管元件的结构。然后，我们使用此信息来更好地了解按照当前树木中流体传输模型的筛管的水力传导率。我们的研究结果表明，茎中韧皮部的解剖结构从当年分支开始发生变化，在那里，它被周环纤维所保护，而到了较老的地方，则缺乏纤维并伴有韧皮部组织中埋藏的乳突管。ose板不仅存在于筛板中，而且存在于韧皮部导管壁中，这使得它们与新鲜切片中的其他韧皮部细胞可辨别。筛管元件的缩放几何形状（包括筛面积的数量和锥形分支之间的孔径）导致了从当年分支到树根的指数电导率。我们对芒果中韧皮部的测量结果与森林木本植物茎中韧皮部结构的测量结果吻合，这意味着尽管进行了农学修剪，但韧皮部的筛管仍会逐渐变细。结果是，