Photosynthetic adaptation to temperature in the red algaeLomentaria baileyanaandLomentaria orcadensis

Abstract

Photosynthetic responses to temperature were examined in tetrasporophytes of Lomentaria baileyana and Lomentaria orcadensis (Rhodophyta). These species have different temperature ranges for growth that reflect seasonal temperature extremes in their natural distributions. L. baileyana is a temperate-subtropical species which grows between 15 and 33°C, whereas L. orcadensis is a boreal-temperate species which grows between 10 and 20°C. Interspecific differences in the photosynthetic responses to temperature were similar to those for growth, suggesting that photosynthesis may determine the temperature range over which Lomentaria tetrasporophytes can grow. Light-saturated rates of photosynthesis were higher in L. orcadensis below 15°C, whereas L. baileyana could photosynthesize at temperatures above 30°C, which inhibited photosynthesis in L. orcadensis. These differences were attributable to genetic adaptations of photosynthetic metabolism because both species were grown under identical conditions for several...