Abstract The uptake of metal ions in soil depends primarily on the soil pH, but the effects of pH on individual heavy metals are not well understood. We found the effects of pH on rice uptake of heavy metals were quite different and the behavior of Zn and Cd were comparable, similar to Mn, but opposite of Fe. The concentration of Zn and Cd increased in plants when the pH was raised from 4.5 to 6.5, and then decreased at a pH of 7.5. Concentrations of Mn increased significantly when the pH was increased to 7.5. Iron plaque on root surfaces induced by high pH was likely related to the absorption and uptake of heavy metal elements, such as Cd and Zn, by the plant. Shoot Cd, Mn, and Zn concentrations were strongly positively correlated with DCB-extractable Cd (R2 = 0.98), Mn (R2 = 0.97), and Zn (R2 = 0.76) on the root surface. By contrast, Fe deposition on the root surface inhibited Fe uptake. Additionally, the pH-dependent expression of OsZIPs and OsNRAMPs affected metal uptake under different pH conditions, including OsZIP1, OsIRT1 and OsNRAMP5. Using a genetic approach that used Osnramp 5 mutants, we revealed the regulation of OsNRAMP 5 expression is the primary factor affecting the concentration of Cd and Mn in rice under different pH. Collectively, our research indicates that the uptake of heavy metals was regulated by pH-depended iron plaque formation and expression of metal transporter genes in rice.

中文翻译：

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水稻重金属吸收受pH依赖性铁斑形成和金属转运基因表达的调控

摘要 土壤对金属离子的吸收主要取决于土壤pH值，但pH值对单个重金属的影响尚不清楚。我们发现 pH 值对水稻对重金属吸收的影响大不相同，Zn 和 Cd 的行为具有可比性，与 Mn 相似，但与 Fe 相反。当pH值从4.5升高到6.5时，植物中Zn和Cd的浓度增加，然后在pH值7.5时降低。当 pH 值增加到 7.5 时，Mn 的浓度显着增加。由高 pH 值引起的根表面铁斑可能与植物对重金属元素（如 Cd 和 Zn）的吸收和吸收有关。枝条 Cd、Mn 和 Zn 浓度与根表面上的 DCB 可提取 Cd (R2 = 0.98)、Mn (R2 = 0.97) 和 Zn (R2 = 0.76) 呈强正相关。相比之下，根表面铁沉积抑制铁吸收。此外，OsZIPs 和 OsNRAMPs 的 pH 依赖性表达会影响不同 pH 条件下的金属吸收，包括 OsZIP1、OsIRT1 和 OsNRAMP5。使用使用 Osnramp 5 突变体的遗传方法，我们揭示了 OsNRAMP 5 表达的调节是影响不同 pH 值下水稻中 Cd 和 Mn 浓度的主要因素。总的来说，我们的研究表明，重金属的吸收受 pH 依赖性铁斑形成和水稻中金属转运蛋白基因表达的调控。我们揭示了 OsNRAMP 5 表达的调节是影响不同 pH 值下水稻中 Cd 和 Mn 浓度的主要因素。总的来说，我们的研究表明，水稻中重金属的吸收受 pH 依赖性铁斑形成和金属转运蛋白基因表达的调控。我们揭示了 OsNRAMP 5 表达的调节是影响不同 pH 值下水稻中 Cd 和 Mn 浓度的主要因素。总的来说，我们的研究表明，水稻中重金属的吸收受 pH 依赖性铁斑形成和金属转运蛋白基因表达的调控。