Nitrogen partitioning and assimilation : methods for the extraction, separation and mass spectrometric analysis of nitrate, amino acid and soluble protein pools from individual plants following 15N labelling
A simple procedure is described for the separation of nitrate, amino acid and soluble protein pools in small volumes of plant extract. Recent developments in mass spectrometry and automated, on-line sample preparation facilitate the precise analysis of the 15N content of samples containing low concentrations of N (≤5 to ≥50μg) with enrichments close to the natural abundance level. When combined, these separation and analysis techniques make it possible to investigate and quantify the relationships between nitrogen uptake, storage, assimilation, and partitioning between discrete pools of N within individual plants, following 15N labelling.