Nonlinear increase of Chlamydomonas cell volume. A: Time course of the daughter cell's volume increase under continuous illumination at 200 μmol m-2 s-1 (data for four cells, shown as "a", "b", "c" and "d"). White arrowheads indicate the beginning of the division phase. B: Volume increase rate as a function of cell volume calculated from data in panel A. C: Volume increase rate versus PAR. D: Relationship between the volume increase rate and duration of the interdivision phase for the cells cultured under continuous illumination with light intensities ranging from 10 to 200 μmol m-2 s-1. The product of the volume increase rate and the interdivision phase duration equals 1.4. Light intensities are as indicated (PAR values are in m-2 s-1).