Paspalum urvillei and Setaria parviflora are two plant species naturally adapted to iron-rich environments such as around iron mines wastes. The aim of our work was to characterize how these two species cope with these extreme conditions by comparing them with related model species, Oryza sativa and Setaria viridis, that appeared to be much less tolerant to Fe excess. Both Paspalum urvillei and Setaria parviflora were able to limit the amount of Fe accumulated within roots and shoots, compared to the less tolerant species. Perls/DAB staining of Fe in root cross sections indicated that Paspalum urvillei and Setaria parviflora responded through the build-up of the iron plaque (IP), suggesting a role of this structure in the limitation of Fe uptake. Synchrotron μXRF analyses showed the presence of phosphorus, calcium, silicon and sulfur on IP of Paspalum urvillei roots and μXANES analyses identified Fe oxyhydroxide (ferrihydrite) as the main Fe form. Once within roots, high concentrations of Fe were localized in the cell walls and vacuoles of Paspalum urvillei, Setaria parviflora and O. sativa whereas Setaria viridis accumulated Fe in ferritins. The Fe forms translocated to the shoots of Setaria parviflora were identified as tri-iron complexes with citrate and malate. In leaves, all species accumulated Fe in the vacuoles of bundle sheath cells and as ferritin complexes in plastids. Taken together, our results strongly suggest that Paspalum urvillei and Setaria parviflora set up mechanisms of Fe exclusion in roots and shoots to limit the toxicity induced by Fe excess.

中文翻译：

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Paspalum urvillei 和 Setaria parviflora，这两种草本自然适应极端富含铁的环境。

Paspalum urvillei 和 Setaria parviflora 是两种自然适应富含铁环境的植物物种，例如铁矿废料周围。我们工作的目的是通过将这两个物种与似乎对 Fe 过量耐受性差得多的相关模式物种稻和狗尾草进行比较，来描述这两个物种如何应对这些极端条件。与耐受性较差的物种相比，Paspalum urvillei 和 Setaria parviflora 都能够限制根和枝条内积累的铁量。根横截面中铁的 Perls/DAB 染色表明雀稗和小花狗尾草通过铁斑 (IP) 的积累作出反应，表明这种结构在限制铁吸收中的作用。同步加速器 μXRF 分析显示存在磷、钙、Paspalum urvillei 根的 IP 上的硅和硫以及 μXANES 分析确定了 Fe 羟基氧化物（水铁矿）是主要的 Fe 形式。一旦进入根部，高浓度的铁就会定位在雀稗、小花狗尾草和水稻的细胞壁和液泡中，而狗尾草则在铁蛋白中积累铁。转移到小花狗尾草枝条的铁形式被鉴定为与柠檬酸盐和苹果酸盐的三铁复合物。在叶子中，所有物种都在束鞘细胞的液泡中积累铁，并在质体中以铁蛋白复合物的形式积累铁。总之，我们的研究结果强烈表明，雀稗和小花狗尾草在根和芽中建立了铁排斥机制，以限制铁过量引起的毒性。