Figure 1.

Scanning electron micrographs showing whole seed and seed coat details of wild-type and mutant seeds. A, Wild-type seed. Note hexagonal epidermal cells with thickened radial cell walls and volcano-shaped columellae in the center of each cell. B, Detail of wild-type seed coat. C, mum4-1 seed. The columellae are absent. D, Detail of mum4-1 seed coat. E, ap2-1 seeds. Seeds are heart shaped and columellae are absent or reduced. F, Detail of ap2-1 seed coat. G, ap2-6 seeds. Seeds are heart shaped and epidermal cells are thin walled, rectangular, and lack columellae. H, Detail of ap2-6 seed coat. I, Mature wild-type ovule. Note similarity in shape to ap2-1 and ap2-6 seeds. Scale bars: A and C, 100 μm; B, 20 μm; D, F, H, and I, 40 μm; E and G, 200 μm.