Abnormal compound starch grain development in flo7 endosperm cells. (A–C) Toluidine blue staining showing the developmental process of wild-type developing endosperm at 12 (A), 15 (B), and 18 (C) DAF, respectively. (D–F) Toluidine blue staining showing the developmental process of flo7 developing endosperm at 12 (D), 15 (E) and 18 (F) DAF, respectively. The insets represent magnified images of the selected areas in (A) to (F). The amyloplasts are outlined with red dashed lines, while starch granules are indicated by red asterisks. Al, aleurone layer. (G, H) Overview of the developing endosperm interior at 18 DAF in wild type (G) and flo7 mutant (H) seeds, respectively. The insets represent the magnified images of the selected areas in (G) and (H). (I) Quantitative comparison of amyloplast numbers at various developmental stages in the wild type and flo7 mutant. Data are given as means±SD (from at least three independent samples) and were compared with wild type by Student’s t-test (*P<0.05, **P<0.01). Bars, 10 μm.