云南蓝果树天然更新困难，物种濒临灭绝，是国家I级重点保护的野生植物和IUCN极度濒危种。全球气候变化和生境破坏导致的干旱，是影响植物天然更新的重要因子，但干旱如何阻碍云南蓝果树的天然更新尚不清楚。本项目采用野外原位生态学实验和室内受控实验相结合的方法，研究干旱导致的水分需求限制和自毒效应加剧对云南蓝果树种子萌发和幼苗生长2个关键环节的影响。具体内容包括：（1）水分冲刷和种子散落位置及其交互作用对种子萌发的影响；（2）PEG法模拟的干旱胁迫对种子萌发和幼苗生长及存活的影响；（3）不同浓度梯度的云南蓝果树不同器官浸提液对种子萌发和幼苗生长及存活的影响；（4）干旱导致的水分需求限制和自毒效应加剧对种子萌发和幼苗生长及存活的交互作用。研究结果能够阐明干旱对云南蓝果树天然更新的影响机制，初步揭示云南蓝果树濒危的原因和机理，为云南蓝果树的有效保存提供科学理论依据，促进全国极小种群野生植物的保护与恢复。

Nyssa yunnanensis is a critically endangered species (IUCN) with natural regeneration difficulties, which has been listed in China's national grade I protection. Global change and habitat destruction induced drought was one of the vital factors hindering natural regeneration of forests. However, the mechanisms by which drought affect natural regeneration of N. yunnanensis were less well known. Here, we carry out paralell in-situ experiments and controlled experiments to study impacts of water demand constraints and aggravated autotoxicity induced by drought on two key steps in natural generation of N. yunnanensis, i.e., seed gemination and seedling growth. The project contains: (1)Effects of water erosion and the position of seeds in the litter on seed germination, seedling growth and survial rate; (2) Effects of PEG simulated drought stress on seed germination, seedling growth and survial rate; (3) Effects of different concentration gradient of different organ extracts on seed germination, seedling growth and survial rate;(4)Interation effects of water demand constraints and aggravated autotoxicity induced by drought on seed germination, seedling growth and survial rate. The results may illuminate impacts of drought on the natural generation of N. yunnanensis and their mechanisms affecting seed germination and seedling survival. Conclusions made from natural regeneration difficulties may partly help reveal endangered reasons of N. yunnanensis. These would provide scientific and theoretic basis for N. yunnanensis conservation program, through whose good demonstration the effective protection of plant species with extremely small populations is to be promoted nationwide.