兰科具有重要的观赏和药用价值，也是重要的保护植物，生态适应性的阐明将有助于其物种资源的保护和利用。根是主要的水分和养分获取器官，对植物的生长及环境适应有重要影响。附生兰科植物生长在水分和养分供应极不稳定的生境中，推测根在其水分和养分适应中具有重要作用，但人们对此的认识甚少。申请者已对兰科植物叶片的生态适应意义开展了系统研究。本项目将以根为重点，利用野外观测和控制实验对地生兰和附生兰进行比较，回答以下四个科学问题：(1)地生兰和附生兰根的形态结构差异及其与环境的关系如何？(2)根的形态结构、水孔蛋白和脱落酸怎样调节兰科植物的水分吸收与输导？(3)根形态结构及共生真菌如何影响兰科植物的养分获取与利用？(4)兰科植物在不同生境中如何协调根、假鳞茎和叶片的功能？通过对这些问题的研究，揭示根在兰科植物水分和养分适应中的作用，为物种资源的保护与利用提供理论依据。发表研究论文5篇，培养研究生3名。

The Orchidaceae family is of great economic importance to floral and pharmaceutical industries as well as one of the most endangered plant taxa. Understanding of how orchids adapt to the environments is essential for their conservation and utilization. Because root is the principal water- and nutrient-absorbing organ, it has a great impact on the growth and ecological adaptation of a plant. Because of low availability of substrates in epiphytic habitats, epiphytic orchids may experience restricted and irregular moisture and nutrient supplies. It is speculated that root may play an important role in adaptation of epiphytic orchids to water and nutrient stresses. However, such knowledge is limited. Over the past 5 years, we have conducted systematic researches on leaf anatomy and physiology of more than 60 members of the Orchidaceae family. Thus, the present project will mainly focus on the structures and functions of roots in terrestrial orchids and epiphytic orchids by using field investigations and controlled experiments. The main research contents include: (1)what are the key differences in root structures and functions between terrestrial orchids and epiphytic orchids? How do the structures and functions of orchid roots respond to the environments? (2)what are the impacts of root structure, aquaporin and abscisic acid on water uptake and transport of orchid plants? (3)what are the influences of root structure and symbiotic fungi on the nutrient uptake and utilization of orchid plants? (4)how do orchid plants coordinate the functions of root, pseudobulb and leaf to cope with environmental stresses. Understanding of the above questions will address the functional roles of root in the adaptation of orchid plants to water and nutrient. The outputs of this project will provide novel knowledge on the conservation and utilization of species resources in Orchidaceae. Five papers including 4 SCI papers will be published, and three graduate students will be trained through implementing this project.