Uptake of glycine by field grown wheat

Abstract

• 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; [13C2], [15N]-glycine and 2-[13C], [15N]-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.