Intermittent air invasion in pervaporating compliant microchannels
Intermittent air invasion in pervaporating compliant microchannels

The physical origin of the intermittent drying of leaves

on the 28 September 2022
Drought is a threat for plants, as it induces gaseous embolisms which can block the circulation of sap in their veins. Recent images at the scale of single leaves have revealed that such embolisms do not invade the vein network smoothly, but rather by intermittent puffs.
We evidenced the origin of this intermittent dynamics, by creating a biomimetic leaf containing the basic elements of real leaves. Crucially, vein networks contain pits, which are nanometric constrictions between sap-conducting cells; we mimicked such pits by inserting constrictions between larger microfluidic channels, embedded within a flexible and permeable material, like the leaves.

We have recovered an intermittent drying dynamics, characterised by an arrest of the embolism inside the constriction, followed by a fast jump at the constriction exit. We have shown that two phenomena drive this dynamics: the pinning of an air/liquid interface on the corners of the constriction, and the channel compliance under the decrease of water pressure during the pinning phase. Therefore, in plants, pits act as capillary traps for embolisms... but only for a limited amount of time.

Keiser, L., Marmottant, P., & Dollet, B. (2022). Intermittent air invasion in pervaporating compliant microchannels. Journal of Fluid Mechanics, 948, A52.
Mis à jour le 28 September 2022