Tamai Kazunori, Ma Jian Feng
Faculty of Agriculture, Kagawa University, Ikenobe 2393, Miki-cho, Kita-gun, Kagawa 761-0795, Japan.
New Phytol. 2003 Jun;158(3):431-436. doi: 10.1046/j.1469-8137.2003.00773.x.
• Rice (Oryza sativa) is a typical Si-accumulating plant and it has been suggested that it has a specific uptake system for silicic acid in the roots. • Here, we characterized this specific system in rice roots. The ability of rice roots to take up Si was much higher than that of other gramineous species. • A kinetic study indicated that Si uptake was mediated by a type of proteinaceous transporter; the K value was estimated to be 0.32 mm, suggesting that the transporter had a low affinity for silicic acid. Si uptake increased linearly with time, but pretreatment with Si did not affect the uptake of Si, suggesting that the system for Si uptake was not inducible. Mercuric chloride and phloretin, significantly inhibited Si uptake, but 4,4'-diisothiocyanato-stilbene-2,2'-disulfonic acid (DIDS) did not. Mercuric chloride and phloretin also inhibited water uptake, but to a lesser extent. Si uptake was unaffected by the presence of boric acid. • Taken together, the data indicate that the uptake of Si by rice roots is a transporter-mediated process and this transporter contains Cys residues but not Lys residues.
• 水稻（Oryza sativa）是一种典型的硅积累植物，有人认为它在根部具有特定的硅酸吸收系统。• 在此，我们对水稻根中的这种特定系统进行了表征。水稻根吸收硅的能力远高于其他禾本科物种。• 动力学研究表明，硅的吸收由一种蛋白质转运体介导；K值估计为0.32毫米，表明该转运体对硅酸的亲和力较低。硅的吸收随时间呈线性增加，但用硅预处理并不影响硅的吸收，这表明硅吸收系统不是可诱导的。氯化汞和根皮素显著抑制硅的吸收，但4,4'-二异硫氰酸根合芪-2,2'-二磺酸（DIDS）则没有。氯化汞和根皮素也抑制水分吸收，但程度较小。硼酸的存在不影响硅的吸收。• 综上所述，数据表明水稻根吸收硅是一个由转运体介导的过程，该转运体含有半胱氨酸残基但不含赖氨酸残基。
