| Abstract: | Electron microscopy of sugarbeet leaves of different ages infected with curly top virus revealed spherical viruslike particles approximately 16 nm in diameter. The particles tended to form clumps and were sometimes associated with fibrils resembling those formed by nucleic acids. The particles were found in nuclei of phloem parenchyma cells. They appeared to arise in the nucleoplasm with no obvious relation to the nucleolus. Nuclear chromatin disappeared concomitantly with the increase in the amount of virus. The nucleolus apparently disintegrated also. Some views indicated that the nuclear envelope breaks down, but, thus far, particles were not detected in the cytoplasm. When particles first appear in a nucleus, a spherical granular inclusion of unknown identity occurs nearby. An amorphous inclusion body is found in the cytoplasm of cells in which the nuclei contain virus. |
