Unlike animals that can run away when their environment is hostile, plants must adapt to the place where they are. In particular, they perceive the deformations induced by mechanical perturbations and alter their growth by a phenomenon called thigmomorphogenesis. This phenomenon has been studied in the case of static, but little is known in the more realistic case of a dynamic load like the wind. Thus, this thesis focuses on the effects of the dynamic growth of plants. The model plant chosen in this study is the unbranched poplar. We first analyse the dynamic behaviour of the poplar. Experiments and finite element calculations have revealed a spatial and frequency organization of the vibration modes induced by gradients of the mechanical properties of the plant. These results are used in a second experiment in which we measure over time the geometric properties of young poplars subjected to various static and dynamic stimulations. We then show that the dominant effect of mechanical stimulation on the growth response is the static component, suggesting a fast accomodation of the plant to the mechanical treatment. Our results also suggest a delocalization of the plant response compared to deformations induced by the perturbation, indicating a transport signal. These elements are finally gathered to amend and supplement the model of perception of strains in plants.
