STRESS TOLERANCE OF PHOTOSYNTHESIS IN SPORELINGS OF THE RED ALGA GRATELOUPIA-DORYPHORA COMPARED TO THAT OF STAGE-III THALLI

More experimental evidence is needed to understand the role of propagu les in macroalgal biology. There are no reports in the literature on t he comparative physiology (e.g. photosynthesis) of sporelings and adul ts. In this paper we report on the variation in photosynthetic paramet ers (maximum photosynthesis, P-max, and efficiency, alpha, and dark re spiration (R-d) Of cultivated young sporelings of the red alga Gratelo upia doryphora (Montagne) Howe under normal conditions and after a sho rt-term incubation at different salinities and temperatures. The resul ts are compared to those for adult Stage III thalli obtained in labora tory culture from the same population of sporelings. The pigment compo sition of sporelings (more chlorophyll a and less phycoerthryn and phy cocyanin than adults) promotes a better photosynthetic performance (hi gher P,, and alpha and lower Rd) under chlorophyll a excitation. The y ounger sporelings were also more tolerant to variations in salinity an d temperature than Stage III, in which the highest Variation in maximu m photosynthesis and dark respiration was observed.