FIGURE 3.

Auxin acts downstream of ABA signaling to promote root hair elongation. (A) Effect of the polar auxin transport inhibitor NPA on root hair elongation. Five-day-old seedlings were grown in solutions containing the indicated concentrations of ABA and/or NPA for 24 h. Scale bar = 2 mm. (B) Root hair elongation of the SAPK10-OE plants in response to ABA and NPA treatments. Five-day-old seedlings were grown in solutions containing the indicated concentrations of ABA and/or NPA for 24 h. Scale bar = 1 mm. (C) Quantification of root hair length of the OsABIL2-OE plants and wild type in response to the exogenous auxin. Five-day-old seedlings were grown in solutions containing 0, 0.1, or 0.5 μM NAA for 24 h. Data are means ± SD. (D) ABA affects the concentration and distribution of auxin indicated by the DR5-GUS reporter. Five-day-old seedlings were grown in solutions containing different concentrations of ABA for 24 h. Scale bar = 2 mm. (E) Close-up view of the long root hair zone of the DR5-GUS line treated with 0.5 μM ABA for 24 h. Images with dark (left) and white (right) backgrounds are shown. (F) The GUS activity in the F₁ seedlings in response to treatment with 2 μM ABA for 24 h. Wild type (DJ) and the OsABIL2-OE plants were crossed with the DR5-GUS line (Zhonghua11 background, ). Five-day-old seedlings were used. Black arrows indicate the accumulation of DR5-GUS in the long root hair zone.