Developing 3-dap endosperms segregating from bsl1/+ plants pollinated with wild-type pollen. (A) Wild-type fully cellular endosperm. (B–D) Segregating bsl1 mutant endosperms showing delayed cellularization—as indicated by the prolonged presence of the central vacuole (arrowheads), occurring irregularly, in a noncentripetal fashion. Endosperm sections were stained with DAPI and viewed under fluorescence microscopy. cv, central vacuole; en, endosperm; nu, nucellus; p, pericarp; z, zygote. Bar, 50 μm.