PISA inhibits root hair formation. A, Root hairs of pin2/eir1, 35S::PIN1, and wild-type (WT) plants treated with PISA. Five-d–old seedlings were cultured for 2 d on vertical agar plates with or without PISA. The values in parentheses represent the concentration of chemicals (micromolar). B, The root hair length and density of pin2/eir1, 35S::PIN1, and wild-type plants treated with PISA. The length and density of root hairs within the 2–4-mm region from root tip were measured. Values are the means ± sd. Asterisks indicate significant differences (n = 8–11, *P < 0.01). C, The root hair formation of wild-type seedlings grown with auxins and auxin transport inhibitors. The values in parentheses represent the concentration of chemicals (micromolar). Bar = 1 mm.