We performed micro-X-ray fluorescence imaging of frozen-hydrated sections of a root of Pteris vittata for the first time, to the best of our knowledge, to reveal the mechanism of arsenic (As) uptake. The As distribution was successfully visualized in cross sections of different parts of the root, which showed that (i) the major pathway of As uptake changes from symplastic to apoplastic transport in the direction of root growth, and (ii) As and K have different mobilities around the stele before xylem loading, despite their similar distributions outside the stele in the cross sections. These data can reasonably explain As reduction, axially observed around the root tip in the direction of root growth and radially observed in the endodermis in the cross sections, as a consequence of the incorporation of As into the cells or symplast of the root. In addition, previous observations of As species in the midrib can be reconciled by ascribing a reduction capacity to the root cells, which implies that As reduction mechanisms at the cellular level may be an important control on the peculiar root-to-shoot transport of As in P. vittata.

中文翻译：

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凤尾根冷冻水合切片中砷的同步加速器微 X 射线荧光成像。

据我们所知，我们首次对蕨类植物根部的冷冻水合切片进行了显微 X 射线荧光成像，以揭示砷 (As) 吸收的机制。在根的不同部分的横截面中成功地观察了 As 分布，这表明（i）As 吸收的主要途径从根生长方向从共生运输转变为质外运输，以及（ii）As 和 K 具有不同木质部加载前石碑周围的迁移率，尽管它们在截面中石碑外的分布相似。这些数据可以合理地解释由于 As 掺入到根的细胞或共质体中，As 减少，在根尖周围沿根生长方向轴向观察和在横截面的内皮层径向观察到。