Effect of Digitonin on Cellular Division

Part III. Fine structural aspects of early phragmoplast development in the absence of an organized mitotic spindle

Abstract

The fine structure of the early developmental stages of anomalous phragmoplasts which occur during spindleless mitoses induced by digitonin in Allium cells was studied. Although spindle formation is suppressed, these anomalous phragmoplasts are functional in that a cell plate is produced. These phragmoplasts appear to develop initially from a proliferation of membranous profiles which are associated with the chromosomes. Later stages in the development of the phragmoplasts are recognized as localized, discrete aggregates of membranous elements situated among the chromosomes. During telophase, the restituting nucleus partially surrounds the aggregations of phragmoplast elements. As a result, one part of the developing cell plate and subsequent cell wall always remains lying in an indented part of the post-mitotic nucleus. It is suggested that the membranous profiles which proliferate among the chromosomes could be derived from fragments of the ruptured nuclear envelope.