The mathematical modelling is performed to study the effect of the permeability of the Casparian bands to water and solutes on the formation of the root pressure. It is shown that the pressure in the xylem vessels which stops the flow across a root cut (root pressure) decreases with increase in the permeability of the Casparian bands to solutes at a fixed hydraulic conductivity. However, if the Casparian bands are permeable to water alone and impermeable to solutes, then changes in the root pressure changes are not observed.
Basing on the information about the structure of the solution and asymptotic estimates in the problem of steady flow across the root, a system of algebraic relations similar to the commonly used compartment models is obtained. As compared with these, the method proposed has an important advantage making it possible to take into account the characteristic features of the anatomical structure of the root and the non-uniformity of the parameter distribution over its cross-section. This enables us to formulate simple finite relationships fitting with sufficient accuracy with the numerical solution obtained within the framework of the continuum model. The application of the approach proposed to solving specific problems is simpler than both the numerical solution based on the continuum model and the solution obtained by asymptotic methods.