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 N-15 LABELING

A simple procedure is described for the separation of nitrate, amino a cid and soluble protein pools in small volumes of plant extract. Recen t developments in mass spectrometry and automated, on-line sample prep aration facilitate the precise analysis of the N-15 content of samples containing low concentrations of N (less than or equal to 5 to greate r than or equal to 50 mu g) with enrichments close to the natural abun dance level, When combined, these separation and analysis techniques m ake it possible to investigate and quantify the relationships between nitrogen uptake, storage, assimilation, and partitioning between discr ete pools of N within individual plants, following N-15 labelling.