Carotenoids and Photoprotection in Crassulacean Acid Metabolism (CAM) Plants

本研究的目的是描述景天酸代谢植物对强光的反应，特别是利用一种新的涉及几种叶片类胡萝卜素的感光过程。这一过程与叶黄素循环中的玉米黄质前体形成玉米黄质有关，有助于安全地清除光合器官中多余的吸收光。叶黄素循环的日常运作将在几种不同类型的处理CAM的植物中得到特征，包括鸭嘴兰、形成玫瑰的丝兰，以及两种拥有肉质叶片的物种，Hoya australis和蕨类植物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发育的叶片和在全光照下发育的叶片来检验，此外，这个问题将通过检查类胡萝卜素成分对光环境中发生在叶或分支中的梯度的适应来解决。叶黄素循环的运作将进一步表现为对高光和低温的组合反应。然后，将在这些在经历强光的栖息地发现的CAM物种中，利用叶黄素循环进行光能耗散，然后将其与C3物种中的情况进行比较。

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.