CELL-CYCLE ANALYSIS OF TUMOUR-DERIVED CULTURES OF CREPIS-CAPILLARIS - KINETIC ANALOGY WITH PROLIFERATION OF ANIMAL TUMOR-CELLS

Analysis of the cell cycle by 3 methods revealed unusual kinetics of proliferation in tumor derived suspensions of C. capillaris. The different methods of analysis yield different estimates of cycle phase durations; such discrepancies were explained in terms of low growth fractions with rapid total cycle transverse. Specifically, confidence in the estimation of G2 duration by the fraction of labeled mitosis analysis, and comparison with shorter G2 estimates obtained by the 2 other methods, suggests that cells drop out in G1. Cells which do not drop out of the proliferative compartment traverse G1 extremely rapidly. Extremely short cell cycle durations in which the G1 phase is virtually non-existent are uncharacteristics of plant cell suspension cultures, in which the G1 phase was previously shown to be extended as compared with meristematic root tip cells. A model was proposed in which a central core of rapidly dividing cells continuously loses cells into a subpopulation of resting or G0 cells with the G1 DNA content. Similarities between plant and animal tumors with respect to cell growth and division are discussed.