CHANGES IN INTENSITY AND SPECTRAL DISTRIBUTION OF FLUORESCENCE EFFECT OF LIGHT TREATMENT ON NORMAL AND

nidulans is variable under prolonged illumination with orange (590 m,I) or blue (440 m,u) light for both normally photosynthesizing and DCMU-poisoned cells. In general, orange light illumination causes an increase of the fluorescence intensity followed by a decrease, while blue light causes an increase until a steady level is reached. Poisoned Anacystis cells show four to eight times larger changes in fluo-rescence intensity than the normal cells; the detailed time course of fluorescence changes is also different in poisoned and normal cells. When algae are cooled to-196°C in light, the light-induced changes in the "steady-state " fluorescence dis-appear in both types of cells. Difference fluorescence spectra, constructed by sub-tracting the fluorescence spectra taken after 5-15 min of illumination from those after 60-90 min of illumination, show a doublet structure of the difference band with a major peak coinciding with the Anacystis emission maximum (685 m,) and a minor peak located at about 693 m,u