Team : MECA

PhD student : LOUF Jean-François

Thesis supervisors :  BADEL Eric , Geoffroy Guena, Yoel Forterre

Dates : October 2021 - December 2015

Description

In nature, plants are constantly subjected to mechanical stresses that affect and modify their growth. A remarkable aspect of this response is that it is not only local but non-local: bending a stem or branch rapidly inhibits growth far from the stressed area. This observation suggests the existence of a signal that can propagate throughout the plant. Among the different hypotheses, it has been suggested that this signal could be purely mechanical, and come from a hydro/mechanical coupling between the deformation of the tissue and the pressure of the water contained in the vascular system of the plant. The objective of this thesis is to understand the physical origin of this coupling through a biomimetic approach. To this end, we developed microfluidic artificial branches with mechanical and hydraulic characteristics similar to those of a tree branch. We showed that the bending of these branches generates a non-zero overall overpressure in the system, which varies as the square of the longitudinal strain. A simple model based on a mechanism analogous to the ovalization of tubes allows us to predict this nonlinear poroelastic response and to identify the key physical parameter driving this pressure response: the bulk modulus of the branch. In light of these results, experiments on tree branches were then conducted and similar signals are obtained and compared to the theoretical model. The similarity suggests the generic nature of the physical mechanism identified for the generation of hydraulic signals in plants.

Link

https://hal.science/tel-02165436v1