Patterns in survival-enhancing mechanisms derived from plant water storage

Internal water storage is of crucial importance for plants under water stress, allowing them to temporarily maintain transpiration higher than root-uptake rate. With the help of a minimalistic model, we investigate the most basic effects that result from the water storage buffering, among them: the time lag between peak daily transpiration and sap flow; the typical reaction time of fluxes to sudden changes in environmental conditions; increased hydraulic safety margin from xylem embolism; and the frequency filtering in the sap flow and water storage recharge. The analytical results derived for each of these phenomena provide insight into the pivotal role of the capacitance in plant survival under water stress. We showcase the predictions and their use by evaluating our model against transpiration and sap flow measurements of a semi-arid pine forest, determining whole-plant and ecosystem-wide characteristics, such as the hydraulic capacitance and hydraulic conductivity.