Characterization of Photosynthetic Rhythms in Marine Dinoflagellates

Abstract

Using data from light-dark cultures of Gonyaulaxpolyedra entrained to a 24-hour cyde, whole ceUi absorption curves and photosynthesishrradiance curves were constructed for various circadian times. While whole celi absorbance and half-satuntion constants of photosynthesis showed no statisticd difference that could be directly related to the photosynthetic rhythm, the initid slope of the photosynthesis-irradiance curve was a time-dependent parameter which altered in direct proportion to the change in photosynthetic capadty. The results indicated a temporal change in the relative quantum yield of photosynthesis, and the circadian rhythmicity of light-limited photosynthesis was establisbed under constant conditions. Circadian rhythmidty was detected in room temperature chlorophyil fluorescence yield. Low temperature fluorescence kinetics also showed fluctuations. The results suggest that regulation of photosynthesis by the biological dock of Gonyaulax may be mediated through the membrane-bound light reactions and a partial explanation of the underlying mechanism is proposed.