The effect of partial protein synthesis inhibition on cell proliferation in higher plants.

Meristematic cells from Allium cepa L. roots can attain a steady state of growth in the presence of anisomycin at concentrations that effectively reduce the rate of protein synthesis. Under these conditions the lengths of cell cycle periods increase but not in the same proportion as the generation time (t). Mitosis is hardly affected and S period is slightly lengthened. G2 increases less in proportion to t, while G1 is extended much higher in proportion to t. Natural synchronous populations have been used to study cell cycle parameters during transition from the physiological steady state to the new one created by the presence of the drug. G2 was the same during transition as during steady-state growth. G1 was much shorter during transition. Average cell mass at division was reduced, and a negative correlation was observed between the length of G2 and the size of the cell at termination of DNA synthesis. We propose that in higher plants, G2 length is regulated by cell mass at completion of DNA synthesis (G2 being shorter in big cells than in small cells), though there is no cell size requirement for mitosis.