Die Tagesperiodik der Photosynthese bei Acetabularia und ihre Abhängigkeit von Kernaktivität, RNS- und Protein-Synthese

Abstract

Normal and enucleate cells of the unicellular marine alga Acetabularia crenulata showed a diurnal rhythm of photosynthesis when cultivated in a 12 hour cycle of light and dark; it is characterized by a maximum and a minimum value of photosynthetic capacity in the middle of the light and the dark period respectively. In cells which had been raised from zygotes in continuous light, and from which the nucleus had been removed by severing the basal rhizoid before exposure to the 12 hour light-dark schedule the typical photosynthetic rhythm occurred. Obviously the nucleus is not essential for the induction and the maintenance of the latter. In aged enucleate cells the rhythm of photosynthesis persisted even 33 days after removal of the nucleus; as synthesis of cellular RNA and proteins had ceased long before it is evident that DNA-dependent RNA synthesis is probably not involved in rhythmicity and in a biological clock mechanism. The observed diurnal rhythm of photosynthesis did not persist in continuous light of low intensity and in darkness.