Silicon (Si) alleviates biotic and abiotic stress in plants and many studies have been conducted in Si uptake by the roots. However, there is limited information about Si translocation during grain filling and the Si transport pathways regulating plant Si uptake. In the present study, we performed a 2-yr field trial on the wild-type rice (Oryza sativa L.) varieties Oochikara and Taichung-65 and their corresponding mutants lsi1 and lsi2. We used multi-collector, inductively coupled plasma mass spectrometry to evaluate Si isotope fractionation by the Lsi1 and Lsi2 transporters. The qualitative isotope fractionation caused by Lsi1 and Lsi2 (δ³⁰Si_Lsi1 and δ³⁰Si_Lsi2) were −2.95 and −2.61‰, respectively, in 2016 and −1.35 and −1.67‰, respectively, in 2017, indicating that transporter Lsi1 and Lsi2 preferentially absorbed ²⁸Si rather than ³⁰Si. Moreover, there was net ²⁸Si enrichment in the mutants, indicating that except for Lsi1 and Lsi2, other Si transport pathways belong to ion channels and electrogenic pumps occur in rice. The unexpected observed decrease in ³⁰Si from the husk to the grain suggests xylem-to-phloem Si transfer during grain filling. Hence, Si isotope fractionation is a useful tool to investigate plant Si uptake and translocation.

中文翻译：

---

同位素分馏法研究低硅水稻突变体中硅的吸收和易位

硅 (Si) 减轻植物中的生物和非生物胁迫，并且已经对根对硅的吸收进行了许多研究。然而，关于籽粒灌浆过程中 Si 易位和调节植物 Si 吸收的 Si 运输途径的信息有限。在本研究中，我们对野生型水稻 ( Oryza sativa L.) 品种 Oochikara 和 Taichung-65 及其相应的突变体lsi1和lsi2进行了为期 2 年的田间试验。我们使用多收集器、电感耦合等离子体质谱法来评估 Lsi1 和 Lsi2 转运蛋白对 Si 同位素的分馏。Lsi1和Lsi2引起的定性同位素分馏（δ ³⁰ Si _Lsi1和δ ³⁰ Si _Lsi2) 分别在 2016 年和 2017 年分别为 -2.95 和 -2.61‰，在 2017 年分别为 -1.35 和 -1.67‰，表明转运蛋白 Lsi1 和 Lsi2 优先吸收²⁸ Si 而不是³⁰ Si。此外，突变体中净富集²⁸ Si，表明除 Lsi1 和 Lsi2 外，其他 Si 运输途径属于离子通道，水稻中存在生电泵。出乎意料地观察到³⁰ Si 从壳到籽粒的减少表明在籽粒灌浆过程中木质部到韧皮部的 Si 转移。因此，Si 同位素分馏是研究植物 Si 吸收和易位的有用工具。