In blue or white light, roots
exhibit negative phototropism (Okada and Shimura, 1992;
Sakai et al., 2000), but red light induces a positive
phototropic response (Figure 1; see also Kiss et al.,2003).
In this paper, we demonstrate that the computer-based
feedback system developed by Mullen et al.(2000) is
useful to study root phototropism since the magnitude of
the phototropic response is enhanced in both blue and red
light (Figures 3, 5)