Figure 1.

Sectors and enlarged framed areas of sectioned oat grains at early (A) and late (B–E) stages of development, showing the appearance and distribution of oil. (A) Sudan black B staining. Oil bodies are grey in the aleurone layer (A) and brown/black in the rest of the endosperm. They occur mainly as discrete entities and sporadically as fused aggregates (arrows) in all endosperm cells, and are most abundant in the subaleurone cells (SA). Starch granules/aggregates (S) are lightly stained. Protein bodies are tiny and brownish in colour (not indicated). (B–E) Toluidine blue staining of a grain sector comprising part of the scutellum and the embryo (E). The magnified framed areas display subaleurone cells (C), endosperm cells close to the scutellum-embryo (D) and inner endosperm cells (E), in which the oil bodies have fused into a matrix that stains green (asterisks), with embedded darkly stained proteins (arrowheads) and blue-contoured starch granules/aggregates (S). Oil is more predominant in the subaleurone cells and in endosperm cells close to the scutellum-embryo region than in the inner endosperm cells. Bar = 30 µm.