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The influence of leaf‐atmosphere NH 3(g ) exchange on the isotopic composition of nitrogen in plants and the atmosphere
Author(s) -
JOHNSON JENNIFER E.,
BERRY JOSEPH A.
Publication year - 2013
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/pce.12087
Subject(s) - atmosphere (unit) , nitrogen , fractionation , chemistry , isotope fractionation , isotopes of nitrogen , environmental chemistry , isotope , ammonia , stable isotope ratio , thermodynamics , chromatography , physics , organic chemistry , quantum mechanics
The distribution of nitrogen isotopes in the biosphere has the potential to offer insights into the past, present and future of the nitrogen cycle, but it is challenging to unravel the processes controlling patterns of mixing and fractionation. We present a mathematical model describing a previously overlooked process: nitrogen isotope fractionation during leaf‐atmosphere NH 3(g ) exchange. The model predicts that when leaf‐atmosphere exchange of NH 3(g ) occurs in a closed system, the atmospheric reservoir of NH 3(g ) equilibrates at a concentration equal to the ammonia compensation point and an isotopic composition 8.1‰ lighter than nitrogen in protein. In an open system, when atmospheric concentrations of NH 3(g ) fall below or rise above the compensation point, protein can be isotopically enriched by net efflux of NH 3(g ) or depleted by net uptake. Comparison of model output with existing measurements in the literature suggests that this process contributes to variation in the isotopic composition of nitrogen in plants as well as NH 3(g ) in the atmosphere, and should be considered in future analyses of nitrogen isotope circulation. The matrix‐based modelling approach that is introduced may be useful for quantifying isotope dynamics in other complex systems that can be described by first‐order kinetics.