The ibr1 ibr3 ibr10 mutant has small cotyledons but normal hypocotyl elongation. A, Mean hypocotyl lengths (+se) of 8-d-old Col-0 (Wt), ibr1-2 ibr3-1 ibr10-1, Ws-2 (Wt), and ilr1-1 iar3-2 ill2-1 seedlings grown under yellow-filtered light at 22°C or 28°C. B, Photograph of 7-d-old Col-0 (Wt), ibr1-2 ibr3-1 ibr10-1, Ws-2 (Wt), and ilr1-1 iar3-2 ill2-1 light-grown seedlings. C, Mean cotyledon areas (+se) of 7-d-old Col-0 (Wt), ibr1-2 ibr3-1 ibr10-1, Ws-2 (Wt), and ilr1-1 iar3-2 ill2-1 light-grown seedlings (n ≥ 33). D, ibr1 ibr3 ibr10 suppresses pen3 enlarged cotyledons. Col-0 (Wt), pen3-4, ibr1-2 ibr3-1 ibr10-1, and pen3-4 ibr1-2 ibr3-1 ibr10-1 seeds were stratified for 3 d at 4°C prior to growth at 22°C under white light. Mean cotyledon areas (±se) of light-grown seedlings during growth following germination (n ≥ 51). Measurements were made using NIH Image software.