Bright Light Does Not Immediately Stop the Circadian Clock of Gonyaulax

Abstract

Circadian rhythms in acid-stimulated bioluminescence and cell division are observed for at least 16 days in bright continuous light (4.5 mW/cm2 or 20,000 lx). The photosynthesis rhythm also fails to stop immediately upon transfer of cell suspensions to bright light. After about 4 wk under these conditions, all rhythms were observed to damp out. In cells transferred from bright light to continuous darkness, the rhythms were reset to about circadian hour 12-14, the phase of the beginning of a normal night.