DNA Synthesis During the Early Division Cycles of Jerusalem Artichoke Callus Cultures

The pattern of DNA replication in relation to the first-divisioncycle of tissue cultures of explants from Jerusalem artichoketubers has been determined by Feulgen photometry of nuclei insections from a single experimental series. After a G₁ phaseof 25 h there is an ‘S’ phase of 14 h followed almostimmediately by mitosis which lasts for 2 h. These figures arecompared with estimated values for the same phases in the second-divisioncycle.