The effects of light and temperature on different phases of the life cycle in the carrageenan producing alga Chondracanthus chamissoi (Rhodophyta, Gigartinales)

Growth of female gametophyte and sporophyte phases of Chondracanthus chamissoi was measured under controlled laboratory conditions, examining effects of different combinations of photon flux density and temperature. Apical segments of both (isomorphic) phases of this alga were cultivated in Von Stosch medium using 12 combinations of photon flux density (PFD, 20 to 120 mu mol m(-2) s(-1)) and temperature (10 to 25 degreesC), comparing the wet weights of thalli produced after 15 days. A difference in the growth rate was noted between the isomorphic phases in which the female gametophyte grew more than the sporophyte at 15 degreesC and above. In both phases. there was a tendency towards increasing growth with increasing temperature, whereas changes in PFD did not produce significant changes in growth in all treatments. However, a significant growth effect due to interaction of the two variables was noted. Within the range of variables studied, temperature was the controlling factor in the growth of Chondracanthus chamissoi mediated by factors of light and life cycle phase. The differential growth of different life cycle phases in response to environmental variables may explain the dominance of one phase over another in natural stands of this alga.