PHOTOSYNTHESIS IN CELL DEVELOPMENT

[Characterization of a synchronous culture of Scenedesmus obliquus, its potential photosynthetic capacity and its photosynthetic quotient during the life cycle]

Using synchronous cultures, the change in the potential photosynthetic capacity and the behavior of the photosynthetic quotient were investigated during the life cycle of Scenedesmus obliquus, strain D 3. Scenedesmus obliquus was synchronized under a light-dark regime of 14:10 hours. The quality of synchrony was demonstrated by complete synchronization, homogeneity, exponential growth, shortest possible life cycle and non-susceptibility of the life cycle to the synchronizing procedure. Furthermore, the synchronous culture was characterized by determination of cell number, dry weight, packed cell volume, chlorophylls a and b and the carotenoids during the life cycle.The potential photosynthetic capacity (as O2 evolution) was measured manometrically and polarographically in white light. This capacity increased from the beginning of the light period until the 8th hour and then declined until the 16th hour, that is until just before release of daughter cell. The percentage difference between the maximum and the minimum of the photosynthetic capacity was the same in the light saturating and light limiting region of photosynthesis. - The photosynthetic quotient was measured by means of Warburg's "indirect method". It proved to be constant throughout the life cycle under light saturating and light limiting conditions. The ratio of O2 evolved to CO2 consumed was just below unity.The results were compared with those of other authors and their significance was discussed. It was concluded that the change in the photosynthetic capacity is inherent in the normal life cycle of green algae and is not a result of the synchronizing light-dark regime.