Visualizing Differences in Plant Water Dynamics with a Simulation Model

Abstract

The model Plant Water Dynamics makes it possible to visualize the dynamic interactions of water fluxes and water potential gradients in plants. Inputs to the model were systematically varied until the outputs closely matched published data for three species that showed contrasting responses to water stress under controlled environment conditions. The analysis revealed that cowpea [Vigna unguiculata (L.) Walp.] plants minimized dehydration and maintained relatively high leaf water potentials by closing their stomates, while sugarbeet (Beta vulgaris L.) and sorghum [Sorghum bicolor (L.) Moench] plants became dehydrated because their stomates were relatively insensitive to decreases in leaf water potential, and because osmotic adjustment delayed stomatal closure. The observation that leaf water potentials were generally lower in sugarbeet than in sorghum was explained by a lower xylem conductance. Stomatal conductance was lower in sorghum than in sugarbeet under well‐watered conditions. This conservative behavior allowed sorghum to delay the onset of a plant water deficit by producing more xylem vessels.