Beyond Cohesion-Tension: Complex dynamics of fluid flow in plant microcapillaries

We present theoretical insights into fluid flow in plant microcapillaries, focusing on water uptake and transport. The cohesion-tension (CT) theory explains this as an interplay between transpiration forces and the cohesion of water in xylem conduits. However, this theory overlooks critical factors like xylem morphology, charged species in sap, and capillary-wall interactions. Our modified framework incorporates these elements through a soft matter and dynamical systems approach. By extending the Lucas-Washburn equation and integrating capillary forces, surface tension corrections, and electrostatic interactions, our model captures the influence of environmental stressors on plant fluid dynamics. We show that capillary wall corrugation, and surface tension corrections based on groundwater electrolytes, significantly affect flow. We also introduce a new dimensionless parameter to govern system stability and further investigate the effect of forcing, with Poincaré sections revealing regimes of quasiperiodic and limit cycle behavior. This study significantly aids in obtaining a clearer understanding of water uptake and sap flow in plants in particular, and fluid flow in microcapillaries in general, under a varied range of surface properties and physical parameters.