The responses of the light-harvesting antenna (phycobiliproteins and chlorophyll a) of the Rhodophycean algae Corallina elongata Ellis et Solander, have been studied in relation to irradiance. Laboratory and field experiments reveal a short-term (0-5 h) accommodation mechanism. After 5 h of light treatment, pigments reach a stable state under constant laboratory conditions. Phycobiliproteins decrease when irradiance increases and chlorophyll a shows the reverse. The mechanism leading to this stable state is oscillatory. The oscillations are dampled through time. Extreme conditions (conditions which induce a decrease in the pigment pool) enhance the oscillatory behaviour. In the field, where irradiance is not constant, the oscillations are enhanced. This behaviour, already described in other related areas of research, allows a swift accommodation of the algae to rapid changes in environmental irradiances. © 1990.
