(a) The primary root phenotypes of Col-0, asa1-1, ERF1ox and ERF1ox asa1-1 seedlings grown on MS medium with either 0 or 0.1 μM estradiol for 5 d. ERF1ox is the transgenic plants expressing ERF1 protein under control of the estradiol-inducible promoter in Col-0 background. Scale bar, 1 cm. (b) qRT–PCR analysis of transcriptions of ERF1. The roots of 5-day-old Col-0, asa1-1, ERF1ox and ERF1ox asa1-1 seedlings grown on MS medium with either 0 or 0.1 μM estradiol were used. Values are mean ± SD of three replicas (***P<0.001. Asterisks indicate Student’s t-test significant differences). (c-d) Primary root length of Col-0, asa1-1, ERF1ox and ERF1ox asa1-1 seedlings grown on MS medium with either 0 or 0.1 μM estradiol were measured at the fifth days. Data shown are average and SD (Values are mean ± SD, n = 20).