Observation of Early Stage of Somatic Embryogenesis from Epidermal Cells of Carrot Hypocotyls by Scanning Electron Microscopy

Abstract

Somatic embryogenesis that occurred directly from carrot epidermal cells was monitored by scanning electron microscopy. Epidermal cells peeled off from hypocotyl tissues were visible as compressed cells, which expanded to become tubular cells. Subsequently, tubular cells divided regularly and “horizontally” to form linear clusters of cells and then these clusters of cells divided “vertically” to begin development. Swelling structures were formed by irregular and oblique division at sites on the linear clusters of cells and these structures continued cell division to form small proembryos. Some cells at the surface of the swelling structures and proembryos expanded in every direction to cover the surface of each structure. These expanding cells appeared to form a surface layer and then cell layers piled up upon one another as the swelling proceeded to a globular-stage embryo via a small proembryo.