From Figs. 8 and 9, the proposed root model could
express the real root elongation adequately. Since
branching of the root is not considered in the model,
the characteristic shape of the root system, as seen in
Fig. 8 (c), is not reproduced in the numerical results.
The shapes of the real root and that of the model
root were compared in terms of fractal dimensions,
since it is known that the root systems could be
analyzed by fractals (Tatsumi, et al., 1989). By
applying the box counting method, it was found that
the fractal dimension for the case shown in Fig. 9 (c)
was 1.0154, which is similar to the dimension of a line,
i.e. 1. Moreover, the calculated fractal dimension for
the experimental result was 0.9901. Since the results
of experiments in Fig. 8 predominantly show straight
growth of the main root, the fractal dimension
(1.0154) from DEM can be interpreted as almost the
same as the fractal dimension from the experiment.