Figure 5. Ammonium reduces the gravitropic response of primary roots.

(A) Primary root curvature in response to gravistimulation. Seedlings were cultured as described in Figure 1A. One day after transferred to 2-layer split plate medium, the seedlings were rotated 90° and root curvature was measured over time. Data represent means ± SD for 16 plants obtained in four replicate experiments. Means for nitrate and ammonium treatment are significantly different: ** p<0.01; *** p<0.001. (B) DR5::GUS expression pattern in root cap in response to gravistimulation. DR5::GUS plants were cultured as described in Figure 1A. Five days after transfer, the seedlings were rotated 90°. Plants were stained with GUS reaction buffer at the indicated times. Red arrow indicates the lower side of the root apex. Images are representative of 10–12 stained plants in three replicate experiments. Scale bars = 50 µm.