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Front. Plant Sci. | doi: 10.3389/fpls.2018.00406

Nitrogen Dilution Curves of Wheat are Less Robust than Usually Assumed: Influence of Crop Water Status, Phenology, Biomass Partitioning, and Water-Soluble Carbohydrates

  • 1South Australian Research and Development Institute, Australia

Nitrogen dilution curves relate a crop’s critical nitrogen concentration (%Nc) to biomass (W) according to the allometric model %Nc = a W-b. This model has a strong theoretical foundation, and parameters a and b show little variation for well-watered crops. Here, we explore the robustness of this model for water stressed crops. We established experiments to examine the combined effects of water stress, phenology, partitioning of biomass, and water-soluble carbohydrates (WSC), as driven by environment and variety, on the %Nc of wheat crops. We compared models where %Nc was plotted against biomass, growth stage and thermal time. The models were similarly scattered. Residuals of the %Nc - biomass model at anthesis were positively related to biomass, stem:biomass ratio, Δ13C and water supply, and negatively related to ear:biomass ratio and concentration of WSC. These are physiologically meaningful associations explaining the scatter of biomass-based dilution curves. Residuals of the thermal time model showed less consistent associations with these variables. The biomass dilution model developed for well-watered crops overestimates nitrogen deficiency of water-stressed crops, and a biomass-based model is conceptually more justified than developmental models.

Keywords: Water stress, carbon isotope discrimination, Phenology, Triticum aestivum, water-soluble carbohydrates.

Received: 30 Nov 2017; Accepted: 14 Mar 2018.

Edited by:

Luis A. Aguirrezabal, National University of Mar del Plata, Argentina

Reviewed by:

Peter Thorburn, Commonwealth Scientific and Industrial Research Organisation (CSIRO), Australia
Sotirios Archontoulis, Iowa State University, United States
Philippe Debaeke, Institut National de la Recherche Agronomique de Toulouse, France  

Copyright: © 2018 Sadras and Hoogmoed. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Victor O. Sadras, South Australian Research and Development Institute, Adelaide, Australia,