Abstract
Rice is a typical Si-accumulating plant and a specific uptake system for silicic acid in rice roots has been suggested. We characterized this specific system in rice roots. Si uptake increased linearly with time, but pre-treatment with Si did not affect the Si uptake, suggesting that the uptake system for Si constantly exists in rice roots. Kinetic study indicated that Si uptake is mediated by a kind of proteinaceous transporter. The Km was estimated to be 0.32 mM, suggesting that the transporter has a low affinity for silicic acid. Mercury chloride, phloretin significantly inhibited the Si uptake, but DIDS hardly affect the Si uptake. Si uptake was also not affected by the presence of 10 times more of boric acid. Taken together, the Si uptake by rice roots is a transporter-mediated process and this transporter contains Cys residues but not Lys residues.
