Auxin signaling underlies Suc-induced hypocotyl elongation and KIN10 regulates expansin gene expression. A, Hypocotyl length of seedlings cultivated with a range of concentrations of the inhibitor of polar auxin transport NPA, under 4-h photoperiods (mean ± se; n = 20). B to E, Suc-induced changes in expansin transcript abundance in elongating wild-type, tps1, and KIN10-ox seedlings under 4-h photoperiods. B and D, EXPA8 and EXPA11 transcript abundance relative to PP2AA3 (mean ± se; n = 3). C and E, The magnitude of Suc-induced change in transcript abundance in each genotype relative to the osmotic control. Data analyzed with ANOVA and posthoc Tukey tests, and with statistical significance indicated using starring (P > 0.05; * = P < = 0.05; ** = P < 0.01; *** = P < 0.001).