Modelling non-uniform soil water uptake by a single plant root.

摘要

The assumption of uniform water flow to the root or uniform water potential at the root surface has been shown to be erroneous. How the non-uniform uptake of water by a single root can be modelled is demonstrated. Differential equations are numerically solved to describe simultaneous water movement in the plant and in the soil. In the plant, boundary conditions are the water potentials at the root surface (psis) and in the xylem at the root base (psib). A set of difference equations describe the flow of water radially through the cortex to the xylem and in the xylem axially upwards to the base. For calculating the water flow in the soil and the values of psis, i.e. the boundary conditions for flow in the root, the finite element method (FEM) is used, the boundary conditions being the flux of water into the plant root and the zero flow across the wall, bottom and surface of a hypothetical soil cylinder surrounding the root.