Phenotypes of zmsmu2-1 mutants. A, Wild-type (left) and zmsmu2-1 (right) seedlings at 20 DAG; note the mutant seedling produced more leaves than wild type. B, A mature zmsmu2-1 mutant plant showing numerous leaves and a poorly branched tassel. C to F, Sagittal longitudinal sections through 16-DAP embryos of wild type (C) and zmsmu2-1 (D–F). The mutant embryos (D and F) are typically smaller than wild type (C). Though many mutant embryos have a single shoot and root meristem (F), like the wild type, some have twin plumules (D) and twin radicles (E). A magnified image of the section in D. S, Scutellum; Cp, coleoptile; R, radicle; Cr, coleorhiza; bars = 0.2 mm.