Fast movements of Mimosa pudica – an osmotic muscle?
Mathieu Rivière
The “touch-me-not” plant Mimosa pudica folds its leaves within seconds in response to mechanical or electrical stimuli, before slowly resetting over tens of minutes.
This reversible motion is classically attributed to osmotic water transport across the pulvinus—a flexible hinge-like organ at the leaf base.
However, this scenario lacks experimental support, and implies that pulvini operate near the physical limits of osmotic transport.
In this seminar, I will present a combination of kinematic, biomechanical, and osmotic experiments that reveal the shortcomings of the classical view.
I will then introduce an alternative mechanism based on local water exchange between cells and adjacent air-filled cavities. Finally, I will discuss ongoing tests of this hypothesis using fast synchrotron x-ray tomography at SOLEIL.
This “air-buffering” mechanism may represent a general strategy for generating rapid hydraulic motions in plants and other non-muscular organisms, bypassing the limitations of long-distance osmotic water transport.