Dissertation Research: Ecological Implications of Inducible C4 Photosynthetic Metabolism in the Submersed Aquatic Angiosperm Hydrilla verticillata

最近在水生植物水螅中发现了一种新型的光合作用。光合作用是植物将二氧化碳和水转化为碳水化合物的生化过程，已被证明是通过两个主要的反应序列发生的，通常被称为C3和C4途径。所有光合作用生物都利用C3途径，然而，包括玉米和甘蔗在内的少数植物也具有C4反应序列，并且是已知产量最高的植物之一。水螅的独特之处在于单个植物根据环境条件从C3光合作用转换到C4光合作用的能力。该项目将在温室和田间研究中利用植物生理学和生态学方法的强大组合，1)量化与田间C4状态相关的环境条件，2)确定诱导C4状态的环境线索，3)比较C3和C4水螅植物的光合作用和生产力。4)确定C4光合作用有利于生长的环境条件；5)确定C4光合作用对该植物整体生产力的重要性。水螅原产于热带非洲和亚洲。它是在20世纪60年代早期由水族馆植物行业引入佛罗里达州的，由于其多产的生长，目前威胁着整个美国南部的淡水资源。因此，阐明其光合生理机制可能为防治这种有害杂草提供重要的知识。这些知识还可以促进育种工作，将理想的C4性状引入C3作物，并可能提高作物产量。此外，了解诱导该植物C4光合作用的环境条件可能有助于了解导致开花植物C4光合作用进化的力量。

A novel type of photosynthesis has recently been discovered in the submersed aquatic plant Hydrilla verticillata. Photosynthesis, the biochemical process by which plants transform carbon dioxide and water into carbohydrate, has been shown to occur by two primary reaction sequences commonly designated as the C3 and C4 pathways. All photosynthetic organisms utilize the C3 pathway, however, a few, including corn and sugar cane, also possess the C4 reaction sequence and are among the most productive plants known. What makes Hydrilla unique is the ability of an individual plant to switch from C3 to C4 photosynthesis depending upon environmental conditions. This project will utilize a powerful combination of plant physiological and ecological methods in both greenhouse and field studies to 1) quantify the environmental conditions associated with the C4 state in the field, 2) determine the environmental cues that induce the C4 state, 3) compare the photosynthetic and productivity rates of C3 and C4 Hydrilla plants, 4) determine the environmental conditions under which C4 photosynthesis benefits growth, and 5) determine the importance of C4 photosynthesis to the overall productivity of this plant. Hydrilla is native to tropical Africa and Asia. It was introduced into Florida during the early 1960's by the aquarium plant industry, and because of its prolific growth currently threatens freshwater resources throughout the southern United States. Therefore, elucidation of its photosynthetic physiology may contribute knowledge important for the control of this noxious weed. Such knowledge may also facilitate breeding efforts to introduce desirable C4 traits into C3 crop plants and possibly increase crop yield. Furthermore, understanding the environmental conditions that induce C4 photosynthesis in this plant may give insights into the forces that resulted in the evolution of C4 photosynthesis in flowering plants.