The growth of a bean (Phaseolus vulgaris L.) root system for 10 d, as simulated by SimRoot, a dynamic simulation model of botanical root systems based on empirical growth parameters. The three-dimensional fractal dimension of the root system was estimated by superimposing three-dimensional grids of varying size on the simulated root system in order to estimate the number of boxes in the three dimensional grid that was intercepted by the simulated root system.