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Theses

Amélioration des modèles de cultures du blé par leurs réponses à la température : Phyllochrone et photosynthèse.

Abstract : Crop models are tools used to predict crop yield in virtual climates. They enable to anticipate the effects of climate change and other constraints and to provide solutions to improve our agriculture. However, current models have a limited consideration of the impact of thermal history on plant capacities, which could be a major limit to their performances. The work presented here provides areas for improving wheat crop models by formalisms of leaf appearance rate and carbon assimilation response to temperature and its variations. The first chapter of this study questions the actual modelling of leaf appearance rate. It is mostly predicted through empirical equations, which do not account for all known effects of temperature, light intensity, photoperiod, atmospheric CO2 concentration and development stage on wheat development rhythm. We present here a new way of modelling wheat leaf appearance rate (LAR) based on plant carbon status. This hypothesis of a carbon-driven development rate was supported by an experiment implying different levels of temperature, light intensity, photoperiod and atmospheric CO2. Results have been translated into an ecophysiological model which showed good performances in predicting LAR in contrasted field growth conditions. The second focus of this thesis was the acclimation of wheat photosynthesis to a temperature change. Experiences carried out in this thesis allowed the development of a data set of assimilation capacities under a large number of temperature change scenarios. We were able to differentiate two types of acclimation mechanisms. The first one is the direct result of temperature effect on the photosynthesis metabolism rate, while the second one reflects the response of stomata to a change of temperature. These hypotheses have been studied deeper in the third chapter of this work, in which these results were reanalyzed through a gas exchange model. The objectives were first to understand the implication of stomatal conductance in wheat carbon assimilation response to long and short-term temperature changes; and then to define the limitation of the model to predict this acclimation. This thesis demonstrates the importance of improving formalisms of temperature effects on development rate and carbon assimilation. It also highlights the limits of empirical models and demonstrates that developing new equations closer to biological knowledge could improve predictions of crop growth models.
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Submitted on : Wednesday, October 13, 2021 - 1:47:44 PM
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  • HAL Id : tel-03376275, version 1

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Maëva Baumont. Amélioration des modèles de cultures du blé par leurs réponses à la température : Phyllochrone et photosynthèse.. Sciences du Vivant [q-bio]. Montpellier SupAgro, 2018. Français. ⟨tel-03376275⟩

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