The dynamics of nitrate (NO3−), a major nitrogen (N) source for natural plants, has been studied mostly through experimental N addition, enzymatic assay, isotope labeling, and genetic expression. However, artificial N supply may not reasonably reflect the N strategies in natural plants because NO3− uptake and reduction may vary with external N availability. Due to abrupt application and short operation time, field N addition, and isotopic labeling hinder the elucidation of in situ NO3−-use mechanisms. The concentration and natural isotopes of tissue NO3− can offer insights into the plant NO3− sources and dynamics in a natural context. Furthermore, they facilitate the exploration of plant NO3− utilization and its interaction with N pollution and ecosystem N cycles without disturbing the N pools. The present study was conducted to review the application of the denitrifier method for concentration and isotope analyses of NO3− in plants. Moreover, this study highlights the utility and advantages of these parameters in interpreting NO3− sources and dynamics in natural plants. We summarize the major sources and reduction processes of NO3− in plants, and discuss the implications of NO3− concentration in plant tissues based on existing data. Particular emphasis was laid on the regulation of soil NO3− and plant ecophysiological functions in interspecific and intra-plant NO3− variations. We introduce N and O isotope systematics of NO3− in plants and discuss the principles and feasibilities of using isotopic enrichment and fractionation factors; the correlation between concentration and isotopes (N and O isotopes: δ18O and Δ17O); and isotope mass-balance calculations to constrain sources and reduction of NO3− in possible scenarios for natural plants are deliberated. Finally, we offer a preliminary framework of intraplant δ18O-NO3− variation, and summarize the uncertainties in using tissue NO3− parameters to interpret plant NO3− utilization.
CITATION STYLE
Liu, X. Y., Koba, K., Makabe, A., & Liu, C. Q. (2014, July 23). Nitrate dynamics in natural plants: Insights based on the concentration and natural isotope abundances of tissue nitrate. Frontiers in Plant Science. Frontiers Research Foundation. https://doi.org/10.3389/fpls.2014.00355
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