Cell volume distribution in Chlorella vulgaris cultures coming out of senescence was measured by flow cytometry every 6 h for 114 h in a full-factorial experiment with initial nitrate (420-4200 mu g NO3-N l(-1)), phosphate (9-186 mu g PO4-P l(-1)), and continuous light (50-330 mu E m(-2) s(-1)) as treatments. The maxima in median and median absolute deviation (MAD) of cell volume were achieved within 6 h of each other and their timing was not a. ected by any treatment. Population speci. c growth rate during the. rst 66 h calculated from volume distribution changes was signi. cantly a. ected by light treatment only ( p = 0.002).