Electron microscopy of isolated tobacco mesophyll protoplasts cultured in vitro

Summary Some ultrastructural changes of tobacco mesophyll protoplasts cultured in vitro were examined under the electron microscope. An early stage of wall regeneration was recognizable after 2 days of culture when randomly oriented fibrils composed of cellulose appeared at the surface of protoplasts. The regenerated walls grew gradually in thickness and the fibrils became oriented parallel to the plasmalemma. During the process of colony formation differentiated mesophyll cells reverted to meristematic ones, accompanying the degeneration of chloroplasts. The significance of these phenomena is discussed.