[Photorespiration in the blue-green alga Anacystis nidulans at different temporatures]

CO2 exchange, (14)CO2 fixation and (14)C-products of Anacystis nidulans (strain L 1402-1) were studied during the induction period at temperatures of +15°C and+35°C. At+15°C the stationary rates of CO2 uptake and respiration were reached directly. At+35°C a maximum of CO2 uptake could be observed at the beginning of the illumination period followed by a lower steady rate of photosynthesis. In the following dark period a CO2 gush appeared at+35°C. The magnitude of the CO2 outburst is relatively independent of the photosyntbetic period. The autoradiographic studies showed that the Calvin cycle is the main carboxylation pathway in Anucystis. At a temperature of +35°C serine was labelled after 20 sec of photosynthesis. At+15°C, on the other hand, a low radio-activity appeared in serine after 5 min of photosynthesis. The results show that photorespiration of Anacystis is stimulated by high temperatures.