Effects of Ultraviolet Microbeam Irradiations on Mitosis Studied in Tradescantia Cells in vivo

抄録

Mitotic spindles of Tradescantia cells were irradiated with an ultraviolet microbeam about 2μ in diameter and its effects on the mitosis were investigated in in vivo observations.
1. A complete suppression of the spindle development occurs, when a polar cap is irradiated in its very young stage and a partial suppression appears when a polar cap is irradiated in its slightly later stage from its appearances.
2. In a complete suppression of the spindle development, a restitution nucleus appears, while in a partial suppression of the spindle a half spindle develops at the intact pole side, inducing blocking and sticking of the chromosomes at the irradiated pole side. When the half spindle transforms into a phragmoplast, both daughter chromosome groups are pushed by the growing of the phragmoplast to the irradiated pole side.
3. Other mitotic aberrations, such as daughter nuclei unequal in size, those with vacuoles, reversion of prophase nuclei into resting ones and occurrence of sticky chromosome bridges are obtained in cells irradiated in various mitotic stages.
4. From the results of UV microbeam irradiations on the polar caps or the spindle poles, their roles and submicroscopic structure were discussed in connection with the mechanism of mitosis.