Water Uptake Model Of Crop Root Systems

This thesis primarily studies differentiate controlling equations of crop root system and numerical simulation of physiological process. The thesis consists of three parts:In the first part, Plant roots uptake water model under non-uniform water po-tential is built according to the mass conservation principle and the water potential’s driving force on water transport in soil-plant system. We assume that the soil water potential obeys linear or exponential functions and build two different water uptake models. We discuss the relation between analytical solutions under non-uniform and uniform water potentials. This model is used to discuss the effect of ratio of the radial resistance to the axial resistance on plant water uptake and to determine the optimal length of root within reasonable range of this ratio.In the second part, we consider the interaction between the pressures in the root and in the soil and build water uptake model with one root based on the model built in the first part. The pressure in soil is unknown and the Green’s function is used to address the pressure in the root.In the third part, we consider the interaction of water transport between the soil and the roots, introduce the root density and the coupling of the main root and the lateral root, calculate the water uptake and velocity, and build the water uptake model of the root system based on the convection-diffusion equation and the root pressure equation. We numerically simulate the effect of water diffusivity on the water distribution in the soil. The simulation results show that the water uptake in the region of lateral roots with larger density is higher than elsewhere and there appears dry zone in the root system. The dry zone will result in root wilting and affect the crop harvest.