Patterns of Mitosis and Differentiation in Cells Derived from Pea Root Protoplasts

Abstract

Mitotic figures of diploid, tetraploid, octaploid and 16-ploid nuclei were observed in cultures of pea root protoplasts whose initial DNA content was apparently 2C and 4C. The distribution of these mitotic figures in the different ploidy levels paralleled the distribution of mitotic figures in the culture of intact root explants and may be related to the hormonal stimulation of mitoses in these cultures. The patterns of the time course of both DNA synthesis and cell division in the protoplast cultures were similar to such patterns observed in the culture of intact root explants, although longer lag periods were observed in the protoplast cultures. Mitotic abnormalities including both chromosome breakage and spindle disfunction were observed in protoplast cultures. A large portion of the cell pairs derived from mitoses (27 % in one experiment) contained Feulgen-positive micronuclei. An accumulation of an as yet unidentified differentiation product termed dense cytoplasmic protoplast derivative was observed. Some of the conditions influencing the development of these derivatives are reported.

The Uptake of Cytokinins by Protoplasts and Root Sections of Brassica campestris

“…Only after 35 h the first fine fibrils appeared at the surface of the protoplasts. In general, regeneration of the cell wall in presence of a cytokinin takes a few days (Landgren 1976).…”

“…Presumable cytokinins are produced by the plasmodia, and trigger host cell division. Cell division of protoplasts is preceded by a rise in nucleic acid synthesis (Landgren 1976). These results initiated a research on early effects of plasmodial extracts or exudates on nucleic acid synthesis of protoplasts of Brassica campestris.…”