目前,大部分橡胶无性系的主枝粗大、树冠略呈圆形至倒圆锥形。粗大的主枝与树干的结合不牢固,树冠重,胶树易断干。理想的分枝习性是主枝细而轻,与树干所成的角度大,象针叶树木麻黄的树型。在北苏门答腊,PB5/51无性系和PBIG实生树植区内可找到针叶树型的胶树。针叶树型无性系的树冠呈圆锥形,树冠表面积大,有利于同化作用。这种有利因素可望提供更大的产胶潜力。 At present, most of the main clones of rubber clout coarse, canopy slightly rounded to inverted conical. The combination of thick main branches and the trunk is not strong, heavy crown, gum tree is easy to dry. The ideal branch habit is the main branch is thin and light, and the angle formed by the trunk, such as coniferous tree ephedra tree. Coniferous gum trees can be found in the North Sumatra, PB5 / 51 clones and PBIG seedlings. Coniferous tree canopy conical crown, crown surface area, is conducive to assimilation. This favorable factor is expected to provide greater potential for gum production.