Cell division periodicity and the nitrate environment of a marine diatom

Cell division periodicity of a marine diatom grown with a 12:12 light/dark cycle was influenced by the manner in which a limiting nutrient (nitrate) was supplied to the external environment of the cell. When nitrate was provided by changing the medium once a day, cell division was periodic, beginning after the nitrate concentration reached the apparent steady state level (about 12 h after the addition). When the same daily ration of nitrate was supplied at 2‐h intervals, periodicity was eliminated in <1 day, and cell division occurred continuously throughout the 24‐h period.