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Aqueous silicate complexes in wheat, Triticum aestivum L .
Author(s) -
CASEY W. H.,
KINRADE S. D.,
KNIGHT C. T. G.,
RAINS D. W.,
EPSTEIN E.
Publication year - 2004
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1046/j.0016-8025.2003.01124.x
Subject(s) - exudate , xylem , silicic acid , silicon , aqueous solution , shoot , silicate , chemistry , nutrient , botany , biology , organic chemistry
The chemical speciation of silicon in xylem exudate from wheat ( Triticum aestivum L.) was examined by 29 Si NMR spectroscopy. Wheat plants were grown to maturity in silicon‐free nutrient medium, and then transferred to a solution containing 0.02 m m 29 Si‐enriched silicic acid. After 30 min the shoots were excised and xylem exudate was collected. Within 10 min the Si concentration of the xylem exudate reached values greatly in excess of that of the starting nutrient solution, eventually reaching levels as high as 8 m m . Silicon‐29 nuclear magnetic resonance spectra indicated the existence of only two Si‐containing species in the xylem exudate, mono and disilicic acid (H 4 SiO 4 o and (HO) 3 Si(µ‐O)Si(OH) 3 o ) in a ratio of approximately 7 : 1. Significantly, there was no evidence of organosilicate complexes. Nevertheless, the efficiency by which the plant concentrates aqueous silicon indicates active mechanisms of silicon transport across root cell membranes.