Figure 1.

ABA affects root gravitropism and auxin relocation. a,b) Quantification of root gravitropic bending under ABA and NaCl treatments. Five‐day‐old seedlings were gravistimulated in the presence or absence of 30 × 10⁻⁶ m ABA (a) or 50 × 10⁻³ m NaCl (b) for 24 h (n ≥ 10 roots). The root growth angle after gravistimulation was measured as described.34 c,d) The effect of ABA on auxin translocation. Five‐day‐old seedlings expressing DR5rev::GFP were transferred to medium supplemented or not with 30 × 10⁻⁶ m ABA for 16 h and then gravistimulated for 4 h in darkness. Fluorescence resulting from DR5rev::GFP was used to monitor auxin translocation during the root gravitropic response (d). The ratio of mean fluorescence intensity of the upper to that of lower side of the root was quantified (c; n = 10 roots). The black arrow indicates the direction of gravity (g). The white arrows mark auxin flow. Scale bar: 60 µm. Error bars represent ± SE (a–c). (∗) P < 0.05, (∗∗) P < 0.01 (Student's t‐test). Three independent experiments were performed with similar results. Representative images are shown.