Nasholm T, Huss-Danell K, Hogberg P
Uptake of glycine by field grown wheat
New Phytologist: 2001 150:59-63
Uptake of glycine, a simple organic nitrogen (N) source, directly from the soil is shown here in a conventionally cropped wheat (Triticum aestivum) field. Wheat plants were harvested after tracer injections into the soil of two forms of dual-labelled amino acid, [C-13(2)], [N-15]-glycine and 2-[C-13], [N-15]-glycine. Uptake of intact amino acid was analysed by stable isotope-, and gas chromatography-, mass spectrometry. Significant increases in 13C were found in root extracts for all glycine-treated plants. Regression analysis of excess 13C VS excess 15N for the two glycine forms showed that at least 20% of absorbed glycine-N was derived from uptake of intact glycine. Gas chromatography-mass spectrometry was used to verify the presence of intact dual-labelled glycine in wheat roots. Results also indicated that glycine decarboxylase had a minor role in metabolism of absorbed glycine in wheat roots. Microbial metabolism in the soil did, however, result in rapid decarboxylation of added glycine. Field-grown wheat takes up glycine directly from the soil, the dependence of agricultural plants on nitrate and ammonium as the only forms of available N is therefore questionable.
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