Characteristics of amino acid uptake in barley
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Plants have the ability to take up organic nitrogen (N) but this has not been thoroughly studied in agricultural plants. A critical question is whether agricultural plants can acquire amino acids in a soil ecosystem. The aim of this study was to characterize amino acid uptake capacity in barley (Hordeum vulgare L.) from a mixture of amino acids at concentrations relevant to field conditions. Amino acids in soil solution under barley were collected in microlysimeters. The recorded amino acid composition, 0–8.2 μM of l-Serine, l-Glutamic acid, Glycine, l-Arginine and l-Alanine, was then used as a template for uptake studies in hydroponically grown barley plants. Amino acid uptake during 2 h was studied at initial concentrations of 2–25 μM amino acids and recorded as amino acid disappearance from the incubation solution, analysed with HPLC. The uptake was verified in control experiments using several other techniques. Uptake of all five amino acids occurred at 2 μM and below. The concentration dependency of the uptake rate could be described by Michaelis–Menten kinetics. The affinity constant (K m) was in the range 19.6–33.2 μM. These K m values are comparable to reported values for soil micro-organisms.
KeywordsActive uptake Affinity constant Amino acids in soil solution Efflux Nitrogen acquisition Organic nitrogen
High-performance liquid chromatography
We would like to thank Margareta Zetherström for support and technical assistance in the laboratory and Bo Ranneby and Jun Yu for statistical advice. Svalöf-Weibull AB kindly provided the barley seeds. This study was financially supported by the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning.
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