Mardi 28 janvier à 10h00 , salle des séminaires IRPHE
The ascent of sap in plants relies on the creation of negative pressure (tension) within their vascular networks, rendering them highly susceptible to bubble nucleation and expansion—a phenomenon known as embolism. Embolism is particularly prevalent under drought conditions and is becoming an increasingly critical issue with the intensification of global warming. The complex structure of plant venation networks, compartmentalized into channels (tracheids or vessel elements) interconnected by constrictions (bordered pits), allows plants to mitigate the spread of embolism. Recent advances in imaging techniques have enabled the observation of embolism propagation in plants, revealing complex "stop-and-go" dynamics across varying temporal and spatial scales.
To investigate the appearance of these complex dynamics in compartmentalized systems, bottom-up experimental approaches have been developed using water-permeable materials subjected to drying. One approach utilizes polydimethylsiloxane (PDMS), which is permeable to water vapor, to study intermittent air invasion in networks of channels linked by constrictions. I developed a theoretical framework to describe the nonlinear dynamics of these systems, accounting for viscous dissipation. This framework enables to determine the scaling of pressure fields and the dynamics of embolism fronts with the system design parameters.
A second approach employs water-swelling hydrogels, which are exceptionally stiff and thus capable of withstanding high negative pressures. I micro-fabricate biomimetic leaves with tightly sealed vessel-like microchannels. I observe the multiscale system response characterized by slow poroelastic water transport and rapid cavitation bubble growth, where inertial, acoustic, and interfacial effects interact.
These studies highlight the intricate interplay of elasticity, hydrodynamics, and capillarity in the embolism of fluidic systems, providing valuable insights into plant functioning and the engineering of biomimetic vascular networks.