Abstract
Tobacco protoplasts were infected with cowpea chlorotic mottle virus and its RNA in the presence of poly-L-ornithine to yield 106 to 107 particles per infected protoplast representing a probable increase in virus concentration of at least 1000-fold by 24 to 72 h after inoculation. The optimum inoculum input for virus was about 0.5 µg/ml and for RNA about 1.2 µg/ml; about 60 and 7%, respectively, of the protoplasts became infected, as judged by fluorescent antibody staining. Data relating to growth curves, inoculum and poly-L-ornithine concentrations, and pH effects are presented along with electron micrographs of sectioned protoplasts.