Compound specific plant amino acid delta 15N values differ with functional plant strategies in temperate grassland

The distribution and natural abundance isotopic (delta(15)N) content of whole tissue and individual amino acids in plants in a temperate grassland were determined using ion chromatography (IC), continuous flow-isotope ratio mass spectrometry (CF-IRMS), and gas chromatograohy-combustion-isotope ratio mass spectrometry (GC-C-IRMS). The results showed that the selected plants (Lolium perenne, Juncus effusus, and Brachythecium rutabulum) differed in their amino acid content and distribution from the parent grassland soil. Bulk and individual amino acid delta(15)N isotope signatures were different between the plants, which concurred with their functional strategy in relation to the relative acquisition of available N sources. The individual amino acid delta(15)N values of histidine and phenylalanine could be used to differentiate between the three plant species.