Effect of Light Intensity on Photosynthetic 14C 0 2 Fixation of A nabaena flos -aquae

The cyanobacterium Anabaena flos-aquae (strain 1444) grown at different intensities o f white light (900. 3500 and 30000 lux) showed changes in the content and com position o f the pigments. Phycocyanin was more affected by high light conditions during growth than chlorophyll a. In comparison to in low white light grown cyanobacteria number o f phycobilisom es and thylakoids decreased under strong light. A diminution o f 14C 0 2 fixation, total amino acid content, glutamic acid and glutamine pools was found in strong white light grown cells. Under these conditions the majority o f l4C-labelling was measured in sugar phosphates. After pressure treatment a marked increase of 14C-incorporation into amino acids could be obtained. Results were discussed with reference to regulation o f buoyancy in Anabaena flos-aquae.