Analysis on root system morphology using a root length density model. II. Examples of analysis on rice root systems

The root system morphology of rice plants (cv.: Koshihikari) grown under control and shaded conditions was analyzed by the root length density model proposed in Part I . The root length densities were simulated under various combinations of the 'root length density constant'(k) and the 'rooting zone radius' (rmax) in the model, and the most suitable values of both parameters were selected so that the simulated root length densities should fit the actual densities. The values of k and rmax thus obtained and other observed data made it possible to calculate the indices relating to the root system morphology, i.e. 'model primary root length', 'coefficient of branching', 'hill primary root length', 'hill total root length', 'area primary root Length', and 'area total root length', which are hardly accessible in field studies. The comparison of these parameters and indices between experimental plots suggested that the root system development was clearly poorer in the shaded plot as had been expected. The simulated root length densities were substantially closer to the actual densities. Although the model was based only on three simple assumptions, the results mentioned above well support its validity.