Exploring the Dual Functionality of Plant Pulvini Using a Physical Modeling Approach.

This article investigates the dual mechanical functionality of plant pulvini—motor organs that alternate between acting as rigid beams supporting leafy appendages and as flexible hydraulic joints enabling movement. Using physical models inspired by the sensitive plant Mimosa pudica, the study demonstrates that this duality arises from the interaction of two key structural features: anisotropically reinforced parenchyma tissues (modeled by sewing thread hoop reinforcements) and a longitudinally stiff but flexurally pliant vascular core (modeled by a flexible plastic strip). The reinforced parenchyma provides circumferential stiffness necessary for generating internal hydrostatic pressure, while the vascular core resists longitudinal extension, together forming a hydrostatic skeleton that enables pulvini to resist external forces when pressurized and bend actively when fluid pressures are redistributed. These findings highlight the importance of structural specialization alongside biochemical mechanisms in pulvinus motor physiology.