Fig. 13. Schematic view of major histological changes in E2748 (1m-5m) and wild-type (1-5) embryos. The underlying colour indicates the sugar status from a high hexose to sucrose ratio (H>S) to a low hexose to sucrose ratio (H<S) changing during development. The E2748 mutation blocks epidermal differentiation. The mutant phenotype is not recognisable in cotyledons of the early stage (1, <50 mg seed weight). Primary differences in epidermal morphology occur during early cotyledon stage (transition from 2m to 3m, 60 mg seed weight) when cells of the outer cell layer of the mutant become vacuolated (3m) instead forming transfer cells (3). Stages 4 (160 mg seed weight) to 5 (260 mg seed weight) represent the main storage phase. Development is arrested in the mutant (4m – 5m). For further details see text.