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

Abstract

The effects of irradiation with an ultraviolet microbeam about 2/[mu] in diameter on the mitotic spindles of staminal hair cells of T. reflexa were investigated. Complete suppression of spindle development occurs when the polar cap is irradiated in very young stages. Partial suppression occurs when the polar cap is irradiated in later stages. Complete supression of spindle development produces a restitution nucleus; partial supression causes a half spindle to develop at the intact pole side, inducing blocking and sticking of the chromosomes at the irradiated pole side. Other mitotic aberrations caused by microbeam irradiations are: daughter nuclei of unequal size, nuclei with large vacuoles, reversion of prophase nuclei into resting ones, and sticky chromosome bridges.