Uptake of glycine by field grown wheat

Abstract

Summary 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 13 C were found in root extracts for all glycine‐treated plants. Regression analysis of excess 13 C vs excess 15 N 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.