The phenotype of primary root meristem size of cep mutants. (A) Representative phenotypes of 6-day primary root meristems. Blue arrowheads indicate the quiescent center, and red arrowheads indicate the boundary of the meristematic zone. Scale bar, 50 µm. (B) Quantitative analysis of the primary root meristem size as indicated bycortex cell number. Data are shown as mean ± SD, n ≥ 25. Asterisks indicate statistically significant differences compared with WT as determined by Student’s t-test. *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001; ns, not significant.