abi4 mutants show the ABA-insensitive phenotype with regard to primary root growth inhibition in response to ABA application. A, The 3-day-old seedlings germinated on 1/2 MS were transferred to 1/2 MS or ABA-containing medium, and the seedlings were harvested 2 days after transfer for photographing. B, The statistics of primary root length of the three genotypes for (A). C, The 4-day-old seedlings germinated on 1/2 MS were transferred to 1/2 MS or ABA-containing medium, and the seedlings were harvested 2 days after transfer for photographing. D, The statistics of primary root length of the three genotypes for (C). The point mutant abi4-1 (CS8104) and the T-DNA insertion mutants abi4-t (SALK_080095), previously described (Shu et al., 2013, 2016b), were employed in this assay. The values are means ± se. In each experiment at least three repeat, and in one repeat, >30 roots per genotype were used. Asterisks indicate significant difference (*P < 0.05, **P < 0.01) according to Student’s t test analysis. ABA concentration is 30 µM. Bar = 1 cm.