Abstract
The synthesis of cauliflower mosaic virus (CaMV) was greatly affected by temperature. The optimum temperature for virus multiplication in turnip plants and their protoplasts was about 20 °C but that for the formation of viroplasm matrix was higher than 20 °C. CaMV multiplication ceased around 33 °C but was restored by reverting to 20 °C. The intensity of vein-clearing symptoms and of formation of viroplasm in turnip plants did not directly relate to the yield of the virus. In protoplasts, normal viroplasm did not seem to be formed and only accumulations of virus particles were observed. This result suggests that the viroplasm matrix was not required for CaMV multiplication.