[The effect of monochromatic light on the extracellular excretion of glycolate and the photorespiration in the blue-green alga Anacystis nidulans]

Abstract

The algae were grown under normal air conditions in a low light intensity (400 lux) and measured in the normal CO2-concentration (0.03 Vol. %). After an illumination period we observed a CO2 gush which is dependent on the temperature and wavelength used during the measurements. At +20°C a CO2 gush occurs only in the blue and far red regions. At +35°C, on the other hand, a CO2 outburst appears over the whole spectrum. The magnitude of the CO2 gush varies with the wavelength used during the light period. On this basis we have measured an action spectrum of photorespiration which is identical with the action spectrum of photosynthetic CO2 uptake.Only at a low temperature (+20°C) and illumination with red light (550 to 651 nm; 10(-s) einsteins/cm(2)·sec) did we find a light induced release of glycolate; in blue (432 and 473 nm; 10(-s) einsteins/cm(2)·sec) and far red light (681 and 703 nm; 10(-8) einsteins/cm(2)·sec) no glycolate excretion occurred. But after addition of α-hydroxy-2-pyridylmethane sulfonate (10(-3)M) glycolate was excreted during illumination with all used wavelengths. The magnitude of glycolate production was nearly the same in all cases. No glycolate excretion occurred at +35°C in the whole region of the spectrum. Here, too, the addition of α-HPMS forced release of glycolate in all wavelengths, indicating that glycolate biosynthesis was occurring.The results are discussed with reference to the physiological behaviour of the algae and activation of photorespiration in blue light. The obtained action spectrum of photorespiration is explained on the basis of a close relationship to photosynthesis.