Physiology of Isoprene Emission from Plants

树木排放的异戊二烯是大气中碳氢化合物的最大来源。异戊二烯在大气中分解迅速，导致低层大气形成、酸雨和蓝色雾霾。只有一些植物产生异戊二烯，它是树木、蕨类植物和热带植物的共同特征。异戊二烯的产生与碳光合作用密切相关，但异戊二烯的形成机制及其在植物中的作用尚不清楚。为了更好地了解异戊二烯的排放量，并预测未来异戊二烯排放量可能发生的变化，将研究生长条件对异戊二烯合成的影响。并对异戊二烯的合成机理进行了研究。先前的研究结果表明，当橡树生长在高二氧化碳的大气中时，异戊二烯的排放速率可以翻倍。在这个项目中，将进一步测试二氧化碳的影响，也将测试被认为是二氧化碳增加的结果的温度升高的影响。将评估对各种生长条件的适应速率。异戊二烯的合成途径将利用研究光合作用的技术进行研究。碳和氢的稳定同位素（非放射性）将用于追踪叶片中异戊二烯合成过程中碳的途径。这些研究之所以重要，是因为异戊二烯在大气化学中的作用，因为异戊二烯的合成可以快速、无损地测量叶绿体内重要的非光合碳代谢（如类胡萝卜素的合成），因为异戊二烯的合成可以影响植物的整体碳收支。

Isoprene emitted from trees is the largest source of hydrocarbons in the atmosphere. Isoprene decomposition in the atmosphere is rapid and causes lower atmosphere formation, acid rain, and blue hazes. Only some plants produce isoprene, it is a common trait in trees ferns, and tropical plants. The production of isoprene is closely associated with the carbon photosynthesis, but mechanism of isoprene formation and its function in plants is unknown. To better understand isoprene emission and to predict changes in isoprene emission which may occur in the future the effect of growth conditions on isoprene synthesis will be studied. The mechanism of isoprene synthesis will also be studied. Previous results indicated that when oak trees are grown in high carbon dioxide atmospheres the rate of isoprene emission can double. In this project the effect of carbon dioxide will be further tested and the effect of increased temperature, believed to be a consequence of increased carbon dioxide, will also be tested. Rates of acclimation to the various growth conditions will be assesed. The pathway of isoprene synthesis will be investigated using techniques developed to study photosynthesis. Stable isotopes (nonradioactive) of carbon and hydrogen will be used to trace the pathway of carbon during isoprene synthesis in leaves. These studies are important because of the role of biogenic isoprene in atmospheric chemistry, because isoprene synthesis can be a fast, nondestructive measure of important, nonphotosynthetic carbon metabolism inside chloroplasts (e.g. carotenoid synthesis), because isoprene synthesis can affect the overall carbon budget of plants.