Auxin distribution in root tips of the wild type (WT), mutants (m1 and m2), and overexpression lines (Ox1–Ox3). Seedlings were grown in nutrient solution containing 0.2 mM NO3− with or without 10 nm NAA application. A, Seminal root length. Plants were grown hydroponically for 14 d in nutrient solution containing 0.2 mM NO3− with/without 10 nm NAA application. B, pDR5::GFP (n = 30) expression in seminal root tips. Seedlings were grown for 7 d in nutrient solution containing 0.2 mM NO3− with or without 10 nm NAA application in agar medium. Bars = 1 mm. C to E, Plants were grown hydroponically for 14 d in nutrient solution containing 0.2 mM NO3−. C, IAA content in root tips of 0 to 0.5 cm and lateral root area of 2 to 8 cm adventitious root from the root tip (n = 7). D, [3H]IAA transport (n = 7). E, Relative expression levels of OsPINs. Relative mRNA levels for individual genes were normalized relative to OsActin (n = 3). Data in A and C to E are means ± se. *, P < 0.05 (Student’s t test) comparing the wild type and other lines. FW, Fresh weight.