CYTOPLASMIC STRUCTURE OF HEALTHY AND TMV‐INFECTED LIVING CELLS

Solberg, R. A., and J. G. Bald. (U. California, Los Angeles.) Cytoplasmic structure of healthy and TMV‐infected living cells. Amer. Jour. Bot. 49 (2) : 149–157. Illus. 1962.—Epidermal leaf hairs from tobacco‐mosaic‐virus‐infected (TMV) tobacco plants were examined with a high‐resolution, phase‐contrast microscope. The infected cells were at a stage, following virus multiplication, when many of them contained crystals and X‐bodies. Attention was concentrated on the background cytoplasm. Structural features were seen that do not usually appear in descriptions of normal cytoplasm. In the parietal cytoplasm of normal cells are relatively homogeneous regions and regions containing what may be interpreted as included portions of the vacuolar system (vesicles). There are also ridges on the vacuolar surface of the cytoplasm representing lines of flow. Thus, the cytoplasm has a varied and changeable topography. The description of normal cytoplasm, apart from such features, corroborates many observations of previous workers; but some of these are included to provide the necessary contrast with diseased cytoplasm. Cytoplasm infected with TMV exhibits increased density and viscosity. Vesicles become isolated, some of the membranous separations retract, cyclosis slows, and vesicles become less elongate as the forces of cyclosis are reduced. Lines of flow in the nonvesiculate cytoplasm may also retract. Typical virus crystals precipitate. X‐bodies form from regions of coagulated cytoplasm and include constituents of the chondriome. The relationship between the vesiculate nature of cytoplasm and the endoplasmic reticulum of electron microscopists is discussed. The presence of non‐aggregated, dispersed virus in cytoplasm is related to the microscopic symptoms of TMV infection.