Abstract
Cytological evidences offered by several authors6, 16) on the leaf cell of Nicotiana glutinosa inoculated with tobacco mosaic virus (TMV) revealed that the degeneration process of the host protoplasm, that began by disorganization of chloroplast and nucleus, followed by accumulation of brown pigment within the degenerated protoplasm, proceeded in parallel with TMV reproduction.
The necrotic lesion of N. glutinosa by TMV infection usually increased in size especially in case of young lesion (Fig. 1). Occasionally, TMV escaped from the necrotic lesion of N. glutinosa, reached the stem-tip passing through inner tissue, without leaving any outer symptom of infection on the stem, and caused stem-tip necrosis (Fig. 2). Then the necrotic lesion spreaded systemically down to the whole plant tissue.
The necrotic lesion of N. glutinosa by TMV infection, that increases in size and even traslocates, is entirely different in its nature from the necrotic lesion formed within the peripheral zone of a hypersensitive wheat variety against the invasion of an incompatible race of the obligate parasite, Puccinia graminis. On the contrary, the necrotic lesion of N. glutinosa may be compared with the diseased spot of a moderately susceptible bean plant affected with Colletotrichum lindemuthianum.
