Some Observations on the Shape and Localization of Different Viruses in Experimentally Infected Plants, and on the Fine Structure of the Host Cells

Abstract

Fragments of leaves from Chenopodium amaranticolor experimentally infected with Arabis mosaic virus have been examined in the electron microscope. In the chlorotic leaf areas, some cells are badly damaged, while others are only slightly altered. Virus particles are seen only in the latter cells. In the less damaged cells the chloroplasts often show protrusions at their ends and seem swollen. Their grana are formed by a reduced number of discs, and the stromatic lamellae are sometimes fragmented. Voluminous cytoplasmic portions with a great number of virus particles are present. These particles have hexagonal shape and a diameter of about 25.5 mμ. They aggregate in concentric layers which form hollow spherical bodies of about 1 μ diameter, inside which is trapped a portion of cytoplasm or a round, electron opaque body. A number of short, bending membranes is frequently seen in these virus-rich cytoplasmic areas. In the more severely damaged cells the chloroplast membrane dissolves, and the chloroplast grana become sparse in the cytoplasm, where they are gradually transformed into electron-opaque bodies. Finally, both the cell membrane and the vacuole are no longer detectable.