Gerard 9521496 The genetic adaptations that enable certain plant species to survive and grow in polar environments where temperatures are near or below 0oC year-round are poorly understood. Low- temperature adaptation is complicated in terrestrial plants by freezing, desiccation and stomatal conductance, and in marine phytoplankton by a variable and unpredictable physical environment. Polar macroalgae provide an experimental system that is not subject to these complications and that is well- suited to the study of cold-adaptation in plants. Cold- adaptation is particularly well developed in Antarctic macroalgae, in which rates of photosynthesis and growth at OoC are comparable to rates achieved at 10-15oC by temperate species. The proposed research uses endemic Arctic and Antarctic seaweeds to answer the question, "What adaptations do polar algae possess that enable them to assimilate carbon and grow rapidly at very low temperatures?" The research focusses on carbon-metabolism characteristics of three closely related polar-temperate pairs of brown algae: Arctic Laminaria solidungula and temperate Laminaria saccharina; Antarctic Desmarestia anceps and temperate Desmarestia aculeata, and Antarctic Himantothallus grandifolius that is related to Desmarestia aculeata and D. anceps, but is morphologically similar to Laminaria saccharina. Carbon-metabolism processes (photosynthesis, respiration and light-independent carbon fixation) that are important in cold-adaptation will be identified in sporophytes of each species pair acclimated to the same temperature. Specific mechanisms of adaptation will be determined by comparing components of the photosynthetic apparatus as well as contents, activities and thermal properties of key enzymes involved in photosynthesis, respiration and light- independent carbon fixation. Comparisons of multiple species pairs and a broad suite of carbon-assimilation parameters will provide a comprehensive analysis of the mechanisms of low- temperature adaptation in algal species endemic to both the Arctic and Antarctic Oceans and increase an overall understanding of low temperature adaptation in all plants.
