Carotenoids and Photoprotection in Crassulacean Acid Metabolism (CAM) Plants

提出的研究目的是表征天冬氨酸代谢（CAM）植物对强光的反应，特别强调涉及几种叶类胡萝卜素的新型光敏过程的应用。这一过程与叶黄素循环中的前体形成玉米黄质有关，有助于安全清除光合器官中过量吸收的光。在几种不同类型的加工CAM的植物中，叶黄素循环的昼夜运作将被表征，包括platyopuntias，形成玫瑰花的丝兰，以及两种具有多肉叶片的物种，Hoya australis和Pyrrossia confluens。类胡萝卜素成分，特别是叶黄素循环，对不同光环境的适应将通过比较在深荫下生长的叶子和在充分阳光下生长的叶子来检验。此外，这个问题将通过检查类胡萝卜素成分对发生在叶子或枝内的光环境中的梯度的驯化来解决。叶黄素循环的运作将进一步被表征为对强光和低温组合的响应。这些CAM物种在高光照环境中发现的光能耗散中对叶黄素循环的利用将与C3物种的情况进行比较。

The purpose of the proposed investigations is to characterize the response of crassulacean acid metabolism (CAM) plants to high light, with a particular emphasis on the employment of a novel photoreceptive process that involves several leaf carotenoids. This process, which is associated with the formation of zeaxanthin from its precursors in the xanthophyll cycle, facilitates the safe removal of an excess of absorbed light in photosynthetic organs. The diurnal operation of the xanthophyll cycle will be characterized in several different types of plants that process CAM, including platyopuntias, rosette-forming yuccas, and two species which possess succulent leaves, Hoya australis and the fern Pyrrossia confluens. The acclimation of the carotenoid composition, and particularly the xanthophyll cycle, to different light environments will be examined through a comparison of leaves which have developed in deep shade versus those which have developed in full sunlight, In addition, this question will be addressed by examining the acclimation of the carotenoid composition to the gradient in the light environment that occurs within the leaves or cladodes. The operation of the xanthophyll cycle will furthermore be characterized in response to a combination of high light and chilling temperatures. The utilization of the xanthophyll cycle in photoreceptive energy dissipation in these CAM species which are found in habitats that experience high light will then be compared with that which occurs in C3 species.