PHOTOSYNTHESIS OF GELIDIUM-SESQUIPEDALE - EFFECTS OF TEMPERATURE AND LIGHT ON PIGMENT CONCENTRATION, C/N RATIO AND CELL-WALL POLYSACCHARIDES

Gelidium sesquipedale, the most important raw material for the extraction of Spanish agar, was studied ecophysiologically. Plant material came from a stressed intertidal system of high temperatures and high photon fluences. The plants were photoresistant and showed saturation of photosynthesis near a PFD of 300-mu-mol m-2 s-1 and a compensation point under 100-mu-mol m-2 s-1. Temperature and irradiance have a synergistic effect on photosynthesis. Pigment concentration decreased with irradiance except in the case of carotenes. Carbon and nitrogen were maximal at maximal photosynthetic rates, and the C:N ratio increased with increasing irradiances together with increases in cell-wall polysaccharides.