EFFECTS OF LIGHT QUALITY AND IRRADIANCE LEVEL INTERACTIONS ON SHORT-TERM PIGMENT RESPONSE OF THE RED ALGA CORALLINA-ELONGATA

Effects of interactions between light quality and irradiance level were tested on photosynthetic pigments of the red intertidal alga Corallina elongata Ellis et Soland. During a short-term accommodation process (0 to 5 h), pigments adapted chromatically to light quality. R-phycoerythrin and R-phycocyanin increases were induced under green light at 180-mu-mol m-2 s-1. In contrast, chlorophyll a increased only under red light at the same irradiance level. In an energy-limited situation, at an irradiance (20-mu-mol m-2 s-1) close to the photosynthetic compensation point of C. elongata, the accommodation process was inhibited and no chromatic response was detected. The use of antibiotics (rifamycin and chloramphenicol) that inhibit chloroplastic protein synthesis revealed that red light acts on phycobiliprotein synthesis in the same way as antibiotics that suppress transcription and translation. The short-term accommodation process involves 'de novo' synthesis of phycobiliproteins. The mechanism of pigment accommodation is discussed in the frame of chromatic adaptation theory.