The Ontogeny of Somatic Embryos of Pennisetum americanum (L.) K. Schum. I. In Cultured Immature Embryos

Abstract

Cell proliferation and the formation of somatic embryos from the scutellum of cultured immature embryos of P. americanum (pearl millet) were examined by light and scanning electron microscopy. The initial region of cell-division activity was in the scutellar node area around the main procambial strand. Cells on the abaxial side of the scutellum, particularly in the coleorhizal half of the embryo, enlarged and became richly cytoplasmic with prominent nuclei. Some of these cells on the periphery of the scutellum underwent internal segmenting divisions and either directly formed embryoids or continued to proliferate and produced an embryogenic callus tissue which could be subcultured. The richly cytoplasmic peripheral cells of the callus, as well as the embryoids, proliferated again to form a secondary callus tissue, organized structures, embryoids, and plants. Increased cell-division activity in the shoot meristem region of some of the embryoids resulted in the formation of broad meristematic zones. Multiple shoot meristems were organized in these embryoids, which gave rise to several plants.