AN EXPERIMENTAL STUDY ON MITOSIS IN THE SOMATIC CELLS OF WHEAT

Abstract

Colchicine markedly interferes with the dynamics of cell division. Mitosis is arrested at metaphase because of the absence of a normal spindle. It is suggested that colchicine prevents the formation of the spindle by inhibiting the viscosity changes of the cytoplasm which accompany mitosis. The daughter chromosomes do not separate normally, but eventually form a single large restitution nucleus which contains double the normal somatic number of chromosomes. Cells may pass through several karyokinetic cycles of this kind without cytokinesis. Separate spindles may be induced by the incompact grouping of chromosomes at metaphase in such cells after recovery. This results in the presence of multi-polar mitoses, which eventually give rise to several daughter cells of various sizes. Ultracentrifuging brings about like end results but its action is somewhat dissimilar. Differences in specific gravity between nuclear and spindle components bring about the displacement of the 2 daughter nuclei from the spindle at anaphase and telophase. The spindle components responsible for the formation of partition walls are usually displaced or inactivated so that binuclear cells result. After recovery these frequently develop multipolar spindles at the next division.