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.

Infection of tobacco mesophyll protoplasts by tobacco mosaic virus

It was proved that the protoplasts prepared from mesophyll of Nicotiana tabacum are infected by tobacco mosaic virus. The infection occurred when purified tobacco mosaic virus particles were added to a protoplast suspension in the presence of poly-L-ornithine. The virus multiplied in these protoplasts to a level of 10(6) virus particles per infected protoplast during 24 hours of incubation. The efficiency of infection was remarkably high, exceeding that by mechanical inoculation of tobacco leaves.