[Two peaks of plastidial DNA-synthesis with different light-dependency in the cell cycle of Euglena gracilis]

In the course of the life cycle of synchronized Euglena gracilis (14: 10 h light-dark cycles) two separate peaks of plastidial DNA synthesis appear. A first maximum (stage I) occurs 1 to 2 hours, after initiation of the light period, the second maximum (stage II) 9 to 10 hours after beginning of the light period. The second maximum of plastidial DNA synthesis precedes the nucleic DNA synthesis by approximately 4 hours. DNA synthesis during stage I also takes place when previously synchronized cells are cultivated in darkness, whereas no DNA synthesis occurs during stage II in the dark.