The Effect of Protoplast Concentration during Inoculation on the Infection of Tobacco Protoplasts

When tobacco protoplasts were inoculated with tobacco rattle virus, the proportion infected was inversely related to the protoplast concentration between 0.5 X 10(5) and 4 X 10(5) per milliliter when the inocula contained phosphate or Tris-HCL buffers, but was independent of protoplast concentration when using citrate buffer. The decrease in infection obtained at high protoplast concentrations in phosphate was diminished by increasing the poly-L-ornithine (PLO) concentration. At usual PLO concentrations, inocula in phosphate produced more infection that those in citrate, but at some suboptimal PLO concentrations the position was reversed. These effects may result from differences in the reaction between PLO and the different buffer anions.