9521341 Davison The study will examine stress-tolerance in two major groups of perennial intertidal macroalgae, the red and brown seaweeds. The research will test the hypothesis that active oxygen is involved in emersion stress of intertidal seaweeds. Damage due to active oxygen will be determined in stress-tolerant and stress- susceptible species exposed to emersion stress by measuring the peroxidation of membrane lipids. Plants will be grown in laboratory culture under conditions that increase their ability to withstand emersion stress. If the research hypothesis is correct, increases in stress tolerance should be associated with increased levels of antioxidants and/or protective enzymes. The proposed research will also determine if intertidal seaweeds express specific stress-proteins in response to emersion stress. The results of the physiological studies will be used to design field experiments to measure the occurrence and importance of sublethal emersion stress in natural communities and to compare the allocation of resources to stress-tolerance in low and high shore species. This research represents one of the first attempts to understand the processes that confer stress tolerance in intertidal seaweeds and will provide valuable insights into the ecology and physiology of these plants. Information on the mechanism of stress tolerance will allow ecologists to assess the costs of stress tolerance and relate these to reproductive output, growth and competitive ability. ***
