Relations between fluorescence and thylakoid structure in Porphyridium cruentum

The increase in chlorophyll a steady-state fluorescence, induced by high NaCl concentration in Porphyridium cruentum in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea, is directly correlated with a significant decrease in thylakoid thickness. It does not appear affected either by alteration of light absorption due to configurational change or by electron transport processes. Oxygen evolution occurs only in intact structures. The interrelationship between membrane structure, oxygen evolution and chlorophyll a steady-state fluorescence is discussed.