<正>对美洲黑杨×欧美杨Ｆ_１代１３个无性系及亲本Ｉ－６９杨的一级分枝特性、生长、干形指标分层次进行系统研究。生长和一级分枝特性在无性系间存在较大差异；相关及通住分析结果表明：上层分枝较直立、中下层分枝趋于平展；上、中层分枝较短，较少；下层分枝较长，较多；上、中层小枝稀少而下层小枝浓密的尖塔形分枝结构是美洲黑杨×欧美杨Ｆ_１无性系的理想冠型。综合生长、干形及一级分枝特性可将该批无性系系统归为三类。

First-order branch characteristics,growth traits and stem form of populus hybrids(1-69*I-45)F1 clones were researched by divided the crown into three parts.Greater variation among clones for growth and branch traits are found. analysis on correlation and path shows that the ideal branch structure of I-69*I-45 F1 clones is:branch angle,branch lenth and branch number gradully increase from upper crown to down crown,less little branch in the upper and middle crown,more in the down crown. In the end of this poper,three types of branch structures ate classified.