tir1 ibr5 morphological phenotypes and auxin response. (A) Adult morphologies of wild-type, ibr5, tir1, and tir1 ibr5 plants. Six-week-old Col-0 (Wt), ibr5-1, tir1-1, and tir1-1 ibr5-1 grown in continuous light are shown. (B) Vascular patterning defects. Cleared cotyledons of 8-day-old Col-0 (Wt), ibr5-1, tir1-1, and tir1-1 ibr5-1 seedlings are shown. Scale bar = 1 mm. (C, D) tir1-1 ibr5-1 auxin-response defects. Lengths of primary roots of 8-day-old 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. tir1 ibr5 roots were significantly longer than tir1 and ibr5 roots on control media and on all auxins tested (P ≤ 0.001) in t-tests assuming unequal variance. Error bars represent standard errors of the means (n ≥ 18).