Fig. 4.

Effects of moisture gradients on root system development of wild-type plants grown in soil. (A) Root systems in the absence of hydrostimulation (Control) and (B) in the presence of hydrostimulation (Hydrostimulated) are shown. The images of root architecture were obtained at time zero and 2, 4, 6, 8, and 10 d after hydrotropic stimulation. These images were merged with images of the water distribution shown in Fig. 2. Blue lines indicate the root regions that elongated during the preceding 2 d of growth (when the previous image was captured). The bottom bar shows water contents as grey scales, which correspond to those of the water distribution map shown above. The root system of a representative seedling is shown for each time point of imaging. Numbers of seedlings used and experiments repeated correspond to those of Table 1. The arrow (g) indicates the direction of the gravitational force.