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Modélisation des interactions entre plantes au sein des peuplements. Application à la simulation des régulations de la morphogenèse aérienne du maïs (Zea mays L.) par la compétition pour la lumière.

Abstract : Crop models aim to simulate mechanistically the physical and biological processes between plants and their environment, to help the reasoning of agricultural practices. Most crop models have been developed in the context of intensive agriculture, and assume the canopy to be an homogeneous entity. Oppositely, the emergence of new agricultural practices, that aim to better take into account the environment, lead to consider the functioning of more heterogeneous systems. The objective of this work was to develop a crop model that consider the canopy as a population of plants interacting together. The basis for this was to combine the modelling of the 3D development of plants with physical models computing the microclimate on the 3D structure. We consider the case of the aerial morphogenesis of corn and its modulation by the competition for light. In a first step, the morphological plasticity of maize was studied experimentally in the field, for contrasting level of competition for light. Competition result in a global reduction of individual plant size together with an increase of the heterogeneity between plants. The analysis of dimensions of organs along the stem further show that the intensity of the reduction varied with the position on the stem, the organ lengths situated at the base of the plant being even increased by competition. These observations justified the choice of open L-systems for implementing, in a second step, the model. This approach allow to deal with a population of plants interacting with their environment, but also to consider explicitly the functioning of individual organs. Microclimatic models for computing light distribution and temperature of organs were adapted from already developed ones. The plant model was elaborated by compiling published data on maize development in standard agronomic conditions. A model of regulation by carbon availability was added and test against its ability to simulate the effects of increasing the density. This model allow to simulate realistically the 3D development of the plant, from standard meteorological data and only 5 genotype parameters. The model also simulate the development of the heterogeneity within the canopy and the reductions of organ dimension along the stem. The first simulations however demonstrate the need for more precise formulation of kinetics of elongation. Thus, in a third step, and because of the lack of data in the literature, we study experimentally the kinetic of elongation of internodes. Two period were identified at the level of an individual internode. In a first period, extension was exponential, and the relative growth rate did not vary with phytomer number. In a second period, elongation was mostly linear, with important variation in both durations and rates with phytomer number. The emergence of sheath above the whorl seems to trigger the start of the second period, and to control indirectly the variation of the elongation rate and the internode final length. It is concluded that the model opens original and already operational perspectives for the interpretation of experimentation, as it allow to situate the period of growth of the different organs and to relate them to the local microclimatic conditions they experienced. The model also allow a direct integration of processes from the organ to the canopy. A better understanding of the regulation of organ size is however needed before using the model for reasoning agricultural practices. The experimental results presented here suggest that environmental triggers, related to the exposition of organs to light or air, could be key to these regulations.
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Contributor : Christian Fournier <>
Submitted on : Thursday, August 7, 2003 - 8:55:41 AM
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Christian Fournier. Modélisation des interactions entre plantes au sein des peuplements. Application à la simulation des régulations de la morphogenèse aérienne du maïs (Zea mays L.) par la compétition pour la lumière.. Ecologie, Environnement. Institut national agronomique paris-grignon - INA P-G, 2000. Français. ⟨tel-00003247⟩

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