Figure 2.

Root gravitropism in Arabidopsis thaliana seedlings. (A) shows a 4 day-old Arabidopsis thaliana seedling (WS ecotype) transferred onto the surface of a 0.8% agar-based 1/2 MS medium (Sedbrook et al., 1999), immediately after reorientation of the plate to position the seedling horizontally (gravistimulation). (B) 33 hours later, both root and hypocotyl have reoriented their growth such that the root is growing vertically downward, and the hypocotyl upward. In both A and B, the gravity vector was directed downward on the picture. (C) Kinetics of root gravitropism after a 90° reorientation similar to the one described in A. The mean root tip angle from the horizontal is shown on the Y axis (in degrees), while the time elapsed since gravistimulation is represented on the X axis (in hours). n = 150 – 200. Error bars represent standard deviations.