MECA

MECA (Effects of MEChanical stresses on the Activity of growth zones )

 Leader: Eric BADEL

Staff

The MECA team is an interdisciplinary Integrative Bio-Mechanics team involving biomechanics, ecophysiologists and molecular physiologists. It analyses the trees' responses to wind and gravity around a generic question: "how do trees manage to stand up for long periods of time when they deploy their architecture in a fluctuating mechanical environment?

In a context of climate change where the frequency of storms could increase at lower current winds, this issue of mechanisms for acclimatization and wind resilience has become crucial.

Our findings show that the support function is active and coupled to growth, allowing i) a dimensioning of the mechanical structure of the plants (height and diameter, rooting) according to current winds during the growth period (thigmomorphogenesis) and ii) postural control (port) via tropical active recovery processes to catch up on possible non-lethal mechanical accidents. It is the combination of these two processes that ensures the plasticity of the coupling between growth and support and allows a durable and acclimatised wearing to the mechanical environment.

A key point of these two processes is the phenomenon of mechanoperception of deformations and inclinations induced by gravity, wind or manipulation.The physical and biological mechanisms involved are analyzed from the scale of the cell to that of the complete 3D architecture of the tree, with a strong concern for multi-scale integration and a constant round trip between experimentation and modelling.

At the macroscopic scale of trees under natural conditions, we build biomechanical perception-response models to identify, prioritize and formalize the physical and biological mechanisms involved in mechanical perception and morphogenetic responses. A particular effort is being made to identify the internal mechanically perceived variables and the spatial and temporal variations in the mechanical sensitivity of the plant as a function of its mechanical history. Work at the molecular level focuses on early molecular events, and in particular on the identification of the gene network determining mechanoperceptive sensitivity and its regulation. In this approach, we often use together methods of morphometry (continuous monitoring of growth rate with or without contact, 3D shape measurements), structural and fluid mechanics (test development, modelling) and molecular biology.

©Photos PIAF