| Abstract: | Microstructure of the mature caryopsis of Digitaria exilis Stapf was studied by light and scanning electron microscopy and compared to chemical composition. The general structure of the caryopsis was similar to that of other grains, notably the millets. Thin bracts (the palea and lemma) and two glumes encased the caryopsis which consists of the thin, compressed layers of pericarp, testa, and cuticle surrounding the endosperm and embryonic tissues. The endosperm consisted of a single layer of aleurone cells and the starchy endosperm. The aleurone layer was thin over most of the starchy endosperm and thicker at the junction of the embryo and starchy endosperm. Aleurone cells contained lipid droplets and protein bodies. The cell contents of the starchy endosperm consisted of simple, polyhedral starch granules, lipid droplets, and protein bodies. Protein bodies were more abundant toward the periphery, and diminished toward the central portion of the starchy endosperm. Cells in certain regions of the embryo contained few, small, spherical starch granules and an abundance of protein bodies. Protein bodies containing phytic acid inclusions were located in the scutellum of the embryo. Compositional analyses revealed that the grain contained 8.2% protein, 2.1% fat, 0.48% fiber, and 1.4% ash. |
