外来植物氮形态偏好的可塑性：机制及与入侵性的关系

氮素有效性是影响外来植物入侵性的重要因素之一。一些入侵植物选择性利用土壤硝态氮或铵态氮，这种氮形态偏好是提高其适合度和竞争能力的重要机制，进而促进入侵。现有研究主要关注氮形态偏好对外来植物入侵性的影响，而对氮形态偏好及偏好程度的变化(即氮形态偏好的可塑性)对入侵性的贡献以及相关机制的研究相对较少。本项目以前人发现的偏好硝态氮和铵态氮的入侵植物(各两种)和共生本地近缘植物为材料，采用野外和室内实验相结合，利用15N标记技术，比较研究：(1)入侵植物与本地植物的氮形态偏好对土壤氮水平和氮形态比例可塑性响应的差异，及其与入侵性的关系，(2)氮形态偏好的可塑性与植物氮同化酶及其同工酶的关系；揭示：(1)入侵植物氮形态偏好的可塑性对其入侵性的贡献，(2)影响入侵植物氮形态偏好可塑性的氮素同化酶机制。本项目对从植物氮素营养视角理解外来植物的成功入侵以及相关的功能酶机制均有重要意义。

Nitrogen (N) availability is one of the important factors affecting invasiveness of exotic plants. Some invasive plants prefer to utilize either nitrate nitrogen (NO3-) or ammonium nitrogen (NH4+) in the soil, which is a vital mechanism to improve its fitness and competitiveness, thus promoting invasion. However, the previous studies have been mainly focused on the preference for inorganic N forms of invasive plants and less considered the change in N form preference and change extent (i.e. the plasticity in N from preference) and the related mechanisms. Based on these above, four invasive plant species (two prefer NO3-, the others prefer NH4+) and their co-occurring native congeners are used in field and pot culturing experiments. Meanwhile, 15N label technique will be applied into the current study. We aim to explore: (1) plastic responses of N from preference and their differences between invasive and their co-occurring native species to different N levels and N forms ratios, and the relationships between plastic responses of N form preference and the invasiveness of invasive plants; (2) relationships of plasticity in N form preference with N assimilation enzymes and their isozymes. By these experiments, two scientific questions will to be answered: (1) the contribution of plasticity in N form preference of invasive plants to their invasiveness; (2) the N assimilation enzyme mechanisms that affect the plasticity in N form preference of invasive plants. This project is of great significance to understand the successful invasion of exotic plants and the related functional enzyme mechanisms from the perspective of plant N nutrition.