Effects of light and nitrogen limitation on the cell cycle of the dinoflagellate Amphidinium carteri

Abstract

Cell cycle phase durations of cultures of Amphidinium carteri in light- or nitrogen-limited balanced growth were determined using flow cytometry. For both types of growth rate limitation, the increases in generation time caused by increasing degrees of limitation were due solely to expansion of the G ₁ phase of the cell cycle. The durations of the S and G ₂ + M phases were independent of growth rate. Furthermore, when cells were deprived completely of light and nitrogen, they arrested in the G ₁ phase of the cell cycle. The results indicate that light- and nitrogen-dependent processes are heavily concentrated in the early part of the cell cycle, while DNA replication and cell division, once initiated, are independent of light or nitrogen supply.