axr1 ibr5 morphological phenotypes and auxin response. (A) Adult morphologies of wild-type, ibr5, axr1, and axr1 ibr5 plants. Six-week-old Col-0 (Wt), ibr5-1, axr1-3, and axr1-3 ibr5-1 grown in continuous light are shown. (B) Vascular patterning defects. Cleared cotyledons of 8-day-old Col-0 (Wt), ibr5-1, axr1-3, and axr1-3 ibr5-1 seedlings are shown. Scale bar = 1 mm. (C, D) axr1-3 ibr5-1 auxin-response defects. Lengths of primary roots of 8-day-old (C) or 9-day-old (D) seedlings grown under yellow-filtered light at 22°C on medium supplemented with various concentrations of IBA (C) or 2,4-D (D) are shown. axr1 ibr5 roots were significantly longer than axr1 and ibr5 on 0 (P ≤ 0.01), 5 (P ≤ 0.001), and 10 (P ≤ 0.001) μM IBA in two-tailed t-tests assuming unequal variance. axr1 ibr5 roots were not significantly different from axr1 roots on tested 2,4-D concentrations. Error bars represent standard errors of the means (n ≥ 15).