BOTANICAL ASPECTS OF CEREALS SA IG 2. 17 Part of a transverse section of a grain of Hard Red Winter wheat, 14.4% protein content, showing concentration of protein in subaleurone endos Protein concentration diminshes towards the central parts of the grain in all cereals P, pericarp curone layer; SA, subaleurone endosper n(Reproduced from N. L. Kent Chem. 1966, 43: 585, by courtesy of the absorptive organ, serving the requirements of Although the fusions of nuclei, occurring dur- the embryonic axis when germination occurs. ing sexual fertilization, and leading to the forma- It consists mainly of parenchymatous cells, each tion of endosperm and embryo respectively, take containing nucleus, dense cytoplasm and oil place approximately at the same time, the develop. bodies or spherosomes. The layer of cells adja- ment of the embryo tissue, by cell division, is cent to the starchy endosperm consists of an relatively delayed When the embryo does enlarge as a palisade. Cells are joined only near their tissue giving rise to a few layers of crushed, empty cells the contents of which have either been Exchange of water and solutes between scutel- resorbed or have failed to develop The crushed lum and starchy endosperm is extremely rapid cells are described variously as the cementing Secretion of hormones and enzymes and absorp- depleted or fibrous layer tion of solubilized nutrients occurs across this bundary during germination. The embryonic axis is well supplied with conducting tissues of a End simple type and some conducting tissues are also The endosperm is the largest tissue of the grain present in the scutellum(Swift and O'Brien, 1970). It comprises two components that are clearlBOTANICAL ASPECTS OF CEREALS 37 p A SA FIG 2.17 Part of a transverse section of a grain of Hard Red Winter wheat, 14.4% protein content, showing concentration of protein in subaleurone endosperm. Protein concentration diminshes towards the central parts of the grain in all cereals. P, pericarp; A, aleurone layer; SA, subaleurone endosperm; I, inner endosperm. (Reproduced from N. L. Kent, Cereal Chem. 1966,43: 5'85, by courtesy of the Editor.) Although the fusions of nuclei, occurring dur￾ing sexual fertilization, and leading to the forma￾tion of endosperm and embryo respectively, take place approximately at the same time, the develop￾ment of the embryo tissue, by cell division, is relatively delayed. When the embryo does enlarge, it compresses the adjacent starchy endosperm tissue giving rise to a few layers of crushed, empty cells the contents of which have either been resorbed or have failed to develop. The crushed cells are described variously as the cementing, depleted or fibrous layer . absorptive organ, serving the requirements of the embryonic axis when germination occurs. It consists mainly of parenchymatous cells, each containing nucleus, dense cytoplasm and oil bodies or spherosomes. The layer of cells adja￾cent to the starchy endosperm consists of an epithelium of elongated columnar cells arranged as a pallisade. Cells are joined only near their bases. Exchange of water and solutes between scutel￾lum and starchy endosperm is extremely rapid. Secretion of hormones and enzymes and absorp￾tion of solubilized nutrients occurs across this boundary during germination. The embryonic axis is well supplied with conducting tissues of a simple type and some conducting tissues are also present in the scutellum (Swift and O'Brien, 1970). Endosperm The endosperm is the largest tissue of the grain . It comprises two components that are clearly