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NEMA: a functional-structural model of nitrogen economy within wheat culms after flowering

Jessica Bertheloot
SAGAH, INRA Angers
on 2011/06/10 at 11:00

Summary

Models simulating nitrogen use by plants are potentially efficient tools to optimize the use of fertilizers in agriculture. Most crop models assume that a target nitrogen concentration can be defined for plant tissues and formalize a demand for nitrogen, depending on the difference between the target and actual nitrogen concentrations. The teleonomic nature of this approach has however been criticized. Here, we describe a mechanistic alternative based on current state of knowledge: NEMA (Nitrogen Economy Model within plant Architecture). NEMA was implemented for a winter wheat plant (Triticum aestivum) after flowering and calibrated on field experiments.

NEMA simulates impacts of incident light and soil nitrogen availability on nitrogen acquisition by roots and use for grain yield. An original feature is to model nitrogen fluxes in an explicitly-described aerial architecture, as driven by RubisCO turnover modulated by local light environment. An emerging property of these local processes is that nitrogen vertical distribution along the stem is predicted to parallel light distribution. Another interesting feature of the model is the use of a pool representing circulating amino acids: nitrogen mass in this pool proved to be a reliable indicator of plant nitrogen status, allowing regulating efficiently root acquisition, remobilisation from vegetative organs, and accumulation in grains in response to nitrogen treatments. Patterns usually observed in field experiments could be interpreted and a sensitivity analysis allowed for the identification of plausible processes limiting for grain yield, protein content, and root nitrogen acquisition, which could be targets for plant breeding.

NEMA is the first functional-structural model implementing a process-based approach for nitrogen economy. This work illustrates the potentialities offered by virtual plants to integrate physiological knowledge and develop comprehensive tools to express genotype x environment interactions. Next step will be to extend NEMA to the whole crop growth cycle.

Bertheloot J, Andrieu B, Fournier C, Martre P. 2008. A process-based model to simulate nitrogen distribution in wheat (Triticum aestivum) during grain-filling. Functional Plant Biology, 35: 781-796.

Bertheloot J, Cournède P-H, Andrieu B. 2011. NEMA, a functional-structural model of nitrogen economy within wheat culms after flowering: I. Model description. Annals of Botany.

Bertheloot J, Wu Q, Cournède P-H, Andrieu B. 2011. NEMA, a functional-structural model of nitrogen economy within wheat culms after flowering: II. Evaluation and sensitivity analysis Annals of Botany.