Fig. 4. Root hair morphology under the N-1-naphthylphthalamic acid treatment.

a Root morphology after being treated with N-1-naphthylphthalamic acid (NPA, 10 μM) for 6 days. Scale bar = 500 μm. b Roots from 0.5× MS control of the same age as those in a. Scale bar = 500 μm. Experiments in a, b were repeated independently at least three times, and representative images are shown. c A schematic illustrating how root hair density and lengths were measured. The number of root hairs in the middle 1 mm segment (shown using a blue segment with a red dot in the middle) of the imaged root represents the root hair density. The lengths of 10 root hairs on each side of the primary root in the middle 1 mm segment were measured to indicate its representative root hair length. Scale bar = 500 μm. d Statistical data showing root hair density and lengths. Ten seedlings were used for the measurement for each line. Data represent mean ± SE and statistically significant differences were analyzed by One-Way ANOVA (one-sided test). p values labeled in the diagram represent the comparisons with WT and letters represent significance at p < 0.01. In box plots, the center line in each box indicates the median. The lower and upper bounds of each box represent the first quartile (25%) and the third quartile (75%), respectively. The bottom and top of whiskers denote the minimum and maximum, respectively. e Transcript levels of RSL4 analyzed by RT-qPCR. Samples were roots grown on NPA or the control (0.5× MS medium without NPA) for 6 days after germinating on 0.5× MS for 4 days. Data represent mean ± SE from three biological replicates. Statistically significant differences were analyzed by two-way ANOVA (one-sided test) and marked with asterisks (*p < 0.05; ***p < 0.001). Asterisks labeled just above the column are for comparing with WT grown under the same condition and those labeled above both columns for each line are for the comparison between two growth conditions (with or without NPA). Source data are provided as a Source Data file.