ANALYSIS OF GROWTH OF TETRAPLOID NUCLEI IN ROOTS OF VICIA FABA

Abstract

Growth of nuclei of a marked population of cells was determined from G1 to prophase in roots of Vicia faba. the cells were marked by inducing them to become tetraploid by treatment with 0.002% colchicine for 1 hr. Variation in nuclear volume is large; it is established in early G1 and maintained through interphase and into prophase. One consequence of this variation is that there is considerable overlap between volumes of nuclei of different ages in the cell cycle; nuclear volume, we suggest, cannot be used as an accurate indicator of the age of the cell in its growth cycle. Nuclei exhibit considerable variation in their growth rate through the cell cycle. of the marked population of cells, about 65% had completed a cell cycle 14–15 hr after they were formed. These tetraploid nuclei have a cell cycle duration similar to that of fast cycling diploid cells of the same roots. Since they do complete a cell cycle, at least 65% of the nuclei studied must come from rapidly proliferating cells, showing that variability in nuclear volumes must be present in growing cells and cannot be attributed solely to the presence, in our samples, of non‐cycling cells.

Heterogeneity of Meristematic Cells ofVicia Faba: Evidence from Nuclear and Chromosome Volumes and from Nuclear Protein Content

“…Even within one phase of interphase, Go, G1, or G2, there is considerable variation in nuclear volumes and values for G, and G2 nuclei may overlap (LYNDON 196 7;MITTWOCH 1968;MuNIZ et al 1970;WHITE and DAVIDSON 1976). We have also found considerable overlap between G, and G2 tetraploid nuclei induced in V. faba (BANSAL and DAVIDSON 1978). The overlap between G1 and G2 nuclear volumes, together with the overlap between prophase and interphase volumes, is occurring between nuclei of different ages in the cell cycle.…”