Abstract：
Sunflower (Helianthus annuus) can potentially be used for uranium (U) phytoremediation. However, the factors influencing the absorption of U and its subsequent distribution within plant tissues remain unclear, including the effect of silicon (Si) which is known to increase metal tolerance. Here, using hydroponics, the effect of Si on the distribution and speciation of U in sunflower was examined using synchrotron-based X-ray fluorescence and fluorescence-X-ray absorption near-edge spectroscopy. It was found that ∼88 % of U accumulates within the root regardless of treatments. Without the addition of Si, most of the U appeared to bind to epidermis within the roots, whereas in the leaves, U primarily accumulated in the veins. The addition of Si alleviated U phytotoxicity and decreased U concentration in sunflower by an average of 60 %. In the roots, Si enhanced U distribution in cell walls and impeded its entry into cells, likely due to increased callose deposition. In the leaves, Si induced the sequestration of U in trichomes. However, Si did not alter U speciation and U remained in the hexavalent form. These results provide information on U accumulation and distribution within sunflower, and suggest that Si could enhance plant growth under high U stress.
摘要：
向日葵（Helianthusannuus）可潜在地用于铀（U）植物修复。然而,影响U的吸收及其随后在植物组织中分布的因素仍不清楚，包括已知增加金属耐受性的硅(Si)的作用。这里,使用水培法，使用基于同步加速器的X射线荧光和荧光X射线吸收近边缘光谱检查了Si对向日葵中U的分布和形态的影响。研究发现，无论如何处理，88%的U都会在根内积累。如果不添加Si,大部分U似乎与根部的表皮结合，而在树叶中，U主要积累在静脉中。添加Si减轻了U的植物毒性，并使向日葵中的U浓度平均降低了60％。在根中，Si增强U在细胞壁中的分布并阻碍其进入细胞，可能是由于call体沉积增加。在树叶中，Si诱导U在毛状体中的螯合。然而,Si没有改变U的形态，U保持六价形式。这些结果提供了向日葵体内U积累和分布的信息，并表明Si可以在高U胁迫下促进植物生长。
