Fine structure of isolated mesophyll protoplasts of tobacco

Protoplasts of palisade cells isolated enzymatically from mature leaves of tobacco were studied with the electron microscope. A cell wall was completely absent, and the chloroplasts contained large inclusion bodies which were believed to be a crystalline form of fraction I protein. The fine structure of the protoplasts was otherwise that of healthy mesophyll cells, indicating that they are in a good physiological state. Some protoplasts were multinucleate as a result of fusion during the isolation process.