1996 Volume 65 Issue 2 Pages 303-308
For the topological analysis of plant root systems, two sets of topological indices have been proposed; the ratios of measured altitude (a) and total external pathlength (Pe) to the expected value of the respective parameter when lateral root branching is assumed to occur randomly {a/E(a), Pe/E(Pe)} and to the maximum value of the respective parameter when all lateral roots emerge from the main root axis (herringbone type) {a/Max (a), Pe/Max (Pe)}. We traced the timecourse changes in these indices with root system development of two rice cultivars grown with the excised root tip culture method, and evaluated their adaptability for the actual complexity of the branching pattern. The a/E (a) and Pe/E (Pe) did not adequately express the progress of complication with root growth and the difference between cultivars in branching pattern because root system size substantially affected the values. On the other hand, changes in a/Max (a) and Pe/Max (Pe) showed close correlation with those in several root developmental characters such as the number and mean branching order of lateral roots (MBO). Thus, we conclude that a/Max(a) and Pe/Max(Pe) are better indices than a/E(a) and Pe/E (Pe) for the topological characterization of morphology in the developmental study of rice root systems.
