Cernusak, Lucas A., Winter, Klaus, and Turner, Benjamin L. (2009) Plant δ15N correlates with the transpiration efficiency of nitrogen acquisition in tropical trees. Plant Physiology, 151 (3). pp. 1667-1676.

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Abstract

Based upon considerations of a theoretical model of 15N/14N fractionation during steady-state nitrate uptake from soil, we hypothesized that, for plants grown in a common soil environment, whole-plant δ15N (δP) should vary as a function of the transpiration efficiency of nitrogen acquisition (FN/v) and the difference between δP and root δ15N (δP − δR). We tested these hypotheses with measurements of several tropical tree and liana species. Consistent with theoretical expectations, both FN/v and δP − δR were significant sources of variation in δP, and the relationship between δP and FN/v differed between non-N2-fixing and N2-fixing species. We interpret the correlation between δP and FN/v as resulting from variation in mineral nitrogen efflux-to-influx ratios across plasma membranes of root cells. These results provide a simple explanation of variation in δ15N of terrestrial plants and have implications for understanding nitrogen cycling in ecosystems.

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