Journal Article

Identification of the Silicon Form in Xylem Sap of Rice (<i>Oryza sativa</i> L.)

Namiki Mitani, Jian Feng Ma and Takashi Iwashita

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 46, issue 2, pages 279-283
Published in print February 2005 | ISSN: 0032-0781
Published online February 2005 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pci018
Identification of the Silicon Form in Xylem Sap of Rice (Oryza sativa L.)

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Rice (Oryza sativa L.) is a typical silicon (Si)-accumulating plant, but the mechanism responsible for the translocation from the root to the shoot is poorly understood. In this study, the form of Si in xylem sap was identified by 29Si-nuclear magnetic resonance (NMR) spectroscopy. In rice (cv. Oochikara) cultured in a monosilicic acid solution containing 0.5 mM Si, the Si concentration in the xylem reached 6 mM within 30 min. In the 29Si-NMR spectra of the xylem sap, only one signal was observed at a chemical shift of –72.6 ppm, which is consistent with that of monosilicic acid. A 1H-NMR study of xylem sap did not show any significant difference between the wild-type rice and mutant rice defective in Si uptake, and the components of the xylem sap were not affected by the Si supply. The Si concentration in the xylem sap in vitro decreased from an initial 18 mM to 2.6 mM with time. Addition of xylem sap to a solution containing 8 mM Si did not prevent the polymerization of silicic acid. All these results indicate that Si is translocated in the form of monosilicic acid through the xylem and that the concentration of monosilicic acid is high in the xylem only transiently.

Keywords: Nuclear magnetic resonance; Rice; Silicon; Xylem; NMR, nuclear magnetic resonance

Journal Article.  3469 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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