Heterogeneity of binucleate cells selected by inhibition of cytokinesis with methyl-3 hydroxy-6 (1H, 3H) quinazoline dione 2–4 (MHQD) in garlic root meristems

Abstract

A binucleate cell population was selected at telophase by inhibition of cytokinesis with MHQD. DNA synthesis in MHQD binucleate cells (and in caffeine-induced binucleate cells for comparison) was demonstrated by a labeling index analysis after continuous or pulse tritiated thymidine ( 3H)-TdR incorporation. In early S-phase, the pulse labeling values were less than corresponding continuous labeling results; the differences are due to fluctuations in DNA precursor incorporation. This periodic uptake, which accounts for the discontinuous synthesis of newly replicated DNA in binucleate cells, is discussed. ( 3H)-TdR labeling and Feulgen microspectrophotometric determinations of relative DNA content suggested that DNA synthesis in MHQD binucleate cells is initiated asynchronously while some binucleate cells stop temporarily or permanently in G 1. The cycling binucleate cells are characterized by a widely varying G 1 duration and consequently by a great dispersion at the S/G 2 and G 2/M transition.