Établissement de courbes de réponse à la température de la croissance du grain de blé Triticum aestivum L.

Abstract : Crop models serve to predict via simulation the effects of climate change on the development and yield of field crops such as wheat, the main cereal for human and animal consumption in Europe. However, today's crop models fail to grasp the effect of high temperatures on wheat grain development, even though due to climate change the frequency of penalizing temperature episodes will increase and notably during wheat grain filling. The aim of this study is to establish temperature response curves of quantities describing wheat grain growth in order to satisfy two objectives: i) better evaluate how increases in temperature effect biological processes involved in grain growth and ii) take into account more rigorously temperature as an input in crop models, particularly by validating whether one can follow grain growth by cumulating daily temperatures (a special case of thermal time), even for high temperatures. To this aim, a field chamber experiment was undergone involving a unique genotype of wheat: plants were submitted to one of the temperatures 15°C, 19°C, 24°C, 29°C, 32°C and 36°C during the entire grain-filling phase. Response variables describing the growth of the grains (dry and wet matter, volume, water quantity and grain density) were monitored by regular extraction of ears between flowering and grain maturity. For each response variable, kinetics were adjusted by a growth function within a nonlinear mixed effects model. The growth functions were selected on 19°C data based on their compatibility to the data, their residual variance and the form of their derivate and were compared by their AIC, before being adjusted on the complete data set in order to extract temperature-dependent statistical parameters. These statistical parameters were used to calculate biological characteristics describing the kinetics (speeds, maximum values, durations…) at each temperature as to form temperature response curves. In the same manner, developmental rates were calculated in order to evaluate the relationship between rate and temperature, which must be linear to validate cumulating daily temperatures to follow development. The present method enabled us to establish coherent temperature response curves of correct orders of magnitude. For example, we found a linear relationship between developmental rate and temperature for dry-matter growth between 15°C and 36°C; however, the linear formalism was not valid for the other response variables. This report also offers a critical analysis of the experimental protocol and improvements for future experiments, and discusses the choices made during our analyses and their alternatives.
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Master Thesis
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Submitted on : Thursday, December 20, 2018 - 11:40:24 AM
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Lauren Inchboard. Établissement de courbes de réponse à la température de la croissance du grain de blé Triticum aestivum L.. Sciences du Vivant [q-bio]. 2018. ⟨dumas-01961904⟩



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