Cytological Study of Tobacco Mosaic, I

Abstract

1. As previously reported (1935) “X-bodies” were often found in microsporogenous cells and tetrads. They were also found in the pollen mother cells in the resting stage, but not observed during reduction division. The process of reduction division showed no irregularities and normal tetrads were formed. Twenty four chromosomes were counted at the metaphase of both the first and second meiotic division.2. The diseased plant produced 88.91 per cent apparently normal pollen grains and 11.09 per cent degenerated ones. On the agar medium containing 5 per cent glucose the apparently normal pollen grains failed to germinate in 36.20 per cent. The healthy plant also produced 88.34 per cent apparently normal pollen grains and 11.66 per cent degenerated ones. In this case, among the apparently normal pollen grains 47.56 per cent could not germinateat all. The degeneration seemed to occur after tetrads were formed.3. The seeds obtained from the cross between diseased and healthy plants and from the self-pollination were abortive in high percentage. This fact is not due to the abnormality of pollen grains or ovules in diseased plants. Whether the female sterility as reported by KOSTOFF is concerned with it or not remained undecided. Most of the normal were ascertained to be germinable.4. The tobacco plant showed no symptoms of mosaic disease, to say nothing of “X-bodies” when inoculated with the expressed juice of diseased plants which boiled for about 15 minutes. Therefore the formation of “X-bodies” is due to the active virus and not to the stimulation of expressed juice which contains inactive virus. When the healthy plant was cultured with the TUKADA-NISIYAMA'S culture solution containing 0.05 per cent of ammonium molybdate it wilted after three days and many yellowish brown granules appeared in the cytoplasm of its cell. These granules gradually gathered into amorphous body which gave an appearance of “X-body”. In the culture solution containing 0.05 per cent of lactic acid it wilted after seven days and its cells showed coagulated cytoplasm. In the solution containing 0.005 per cent of ammonium molybdate or lactic acid the cells remained quite normally. Further, in the culture solution containing 0.001 per cent of potassium iodide or sodium iodide, they showed no changes in the cytoplasmic contents in about one month.