Figure 7.

Saltatory Statolith Movements and Rapid Response of Statoliths Displayed at 1-s Time Intervals during Reorientation up to 15° in Arabidopsis (Ws).

(A) to (D) Statoliths exhibiting short-range, randomly oriented saltatory movements. Shown are the DIC micrographs of a central S2 columella cell (top images) and the retraced cell (bottom images). The time-resolved positions of the statoliths (transparent gray) during 1-s time intervals (t) without root reorientation (Θ = 0°) are superimposed on the starting position of the statoliths (t = 0 s; black).

(E) to (H) Statolith aggregates show an instantaneous response within <1 s to short-range reorientations. Shown are the DIC micrographs of a central S2 columella cell (top images) and the retraced cell (bottom images). The time-resolved positions of the statoliths (transparent gray) during 1-s time intervals (t) up to an angle of incidence Θ = 15° with the gravitational force are superimposed on the position of the statoliths before reorientation (t = 0 s; black). The net movement of statoliths (white arrows) is away from the ER interface toward the central cytoplasm. The gravity vector (g), the orientation of the root tip (diamond-shaped arrow) within the gravity field, and the position of the cell nucleus (N) at the proximal end of the columella cell are as indicated. Bar = 5 μm.