Genetic Adaptation to High Temperature in a Marine Alga

温度是植物分布的主要决定因素。每个物种的耐受极限是由遗传决定的，并可以通过遗传适应来扩大。陆地被子植物对高温的适应涉及生理生化特性的改变，导致光合作用的热稳定性和净固碳。通过比较来自长岛海湾的耐高温生态型海带海带和来自缅因州的非适应海藻种群的特征，将研究海藻的适应机制。将详细研究每个生态型的光合作用对温度响应的适应性变化，包括热损害的时间依赖性和可逆性，以及高温诱导的光抑制。还将比较每种植物的暗呼吸和光呼吸的热反应。光合作用中最敏感的成分--光系统II的热稳定性将利用叶绿素荧光技术进行检测。关键的光合酶和呼吸酶的适应性变化将通过比较体外的热性质和比较暴露在超适温度下的植物的活性来确定。这些结果将提供迄今为止关于海藻可以扩大其温度耐受性的机制的最全面的信息，从而提供其地理和环境范围。

Temperature is a primary determinant of the distribution of plants. Tolerance limits of each species are genetically determined, and can be extended through genetic adaptation. High-temperature adaptation in terrestrial angiosperms has been shown to involve changes in physiological and biochemical traits, resulting in greater thermal stability of photosynthesis and net carbon- fixation. Mechanisms of adaptation will be examined in a marine alga by comparing traits of a high-temperature tolerant ecotype of the kelp, Laminaria saccharina, from Long Island Sound and a non adapted population from Maine. Adaptive changes in photosynthesis vs. temperature responses of each ecotype will be examined in detail, including time-dependence and reversibility of heat damage, and high-temperature induced photo inhibition. Thermal responses of dark respiration and photo respiration will also be compared for each plant. Thermal stability of photosystem II, the most heat- sensitive component of photosynthesis, will be examined using chlorophyll fluorescence techniques. Adaptive changes in key photosynthetic and respiratory enzymes will be determined by comparing thermal properties in vitro and by comparing activity in plants exposed to superoptimal temperatures. The results will provide the most comprehensive information to date about mechanisms by which a marine alga can extend its temperature tolerance and, thereby, its geographic and environmental ranges.