A MODEL FOR WATER-UPTAKE IN PLANTS

A model is developed to describe water flow through soil containing ro ots. The governing equation is Richard's equation with a sink term rep resenting extraction of water by the root system. Radial and axial flo w in the root system is modeled as a resistance network, with radial r esistances obtained approximately from a single root radial model and axial resistances obtained using the Hagen-Poisuille law. The analysis leads to a nonlinear parabolic partial differential equation coupled with a second order two-point boundary value problem. A maximum princi ple is proved for the system, giving uniqueness and continuous depende nce on the data. Results of simulations are presented. (C) Elsevier Sc ience Inc., 1997.