SIZ1 promotes apical hook development. A) Apical hook phenotype of 3-d-old dark-grown Col-0, siz1-2, and SIZ1pro:SIZ1-GFP siz1-2 (SSG) seedlings. Scale bars, 1 mm. B) Quantification of apical hook curvature from seedlings shown in A). Data represent means ± Se from 3 replicates, with each replicate consisting of at least 12 seedlings. Different lowercase letters indicate significant differences (P < 0.05) based on 1-way ANOVA followed by Fisher's Lsd test. C) Apical hook phenotypes of Col-0, siz1-2, and SSG seedlings. The seedlings were grown on half-strength MS medium in darkness for 3 d and then transferred to light (D to L) for the indicated times. Scale bars, 1 mm. D) Quantification of apical hook curvature from seedlings shown in C). Data represent means ± Se from 3 replicates, with each replicate consisting of at least 12 seedlings. Percentages represent the decrease in apical hook angle (light-induced angle/angle before light exposure). Different lowercase letters indicate significant differences (P < 0.05) based on 2-way ANOVA followed by Fisher's Lsd test.