<正>以七叶树（Aesculus chinensis Bunge）和红花七叶树（A. pavia L. ）1年生苗木为材料，经不同低温处理后，用透射电子显微镜观察其顶芽基部组织细胞超微结构的变化。结果表明：七叶树顶芽基部组织细胞死亡的基点温度和冷冻时问分别为-18℃条件下冷冻72h、-30℃条件下冷冻24～72h和-70℃条件下冷冻24h。此时细胞超微结构表现为大部分细胞内含物降解，空泡化，细胞质解体，少数细胞虽未解体，但核膜巳变得模糊不清；红花七叶树顶芽基部组织细胞死亡的基点温度和冷冻时问分别为-18℃条件下冷冻168h、～3Oc条件下冷冻168h和-70℃条件下垮冻24h。此时细胞超微结构表现为细胞出现质壁分离现象，细胞结构不清晰。细胞质解体，核凝聚。质膜上合较多电子致密的黑颗粒。从细胞超徽结构的比较可以看出，红花七叶树的抗寒能力明显大于七叶树。

In order to study the interception law of forest canopy to precipitation, based on the theory of stored-full runoff in watershed, a new model of precipitation interception was developed from mechanism of forest canopy intercepting rainfall. The determining method of model parameters was produced by combining with observation data of two woodlands. The effectiveness of the model was also examined. The results showed that calculation values well fit observation values well. Therefore, the model revealed a general law and characteristics of forest canopy interception to rainfall. This model could be applied to forecast calculation of interception when model parameters are given.