Top advantage, also called polarity. Refers to the upper and top branches of the same branch, which grow strongest; The closer the bud is to the top, the more upright the branches are, the more vigorous the growth is, and the phenomenon of downward weakening in turn is called apical dominance or apical dominance (Figure 5).

Fig. 5 advantages of stem tip

Using or controlling the top advantage is a technical measure often used in fruit tree pruning. Take advantage of the top. Can improve the spatial position of branches and buds; The growth potential of trees can be enhanced by using the strong branches and strong buds in the dominant position. In order to enhance the growth of weak branches, measures can be taken to increase the branch angle, take strong branches and strong buds as the leading factor, and cut lightly and put long. In order to balance the growth of the tree, when it is necessary to control the top advantage of a single branch, pruning measures such as reducing the spatial position of the branch bud or reducing the opening angle of the branch can be taken to alleviate the growth of a single branch and balance the tree. For vigorous branches, pruning can be used to suppress their top advantage; For weak branches, try to make use of the pruning method of its top advantage. This pruning method can achieve a good effect of restraining the strong and helping the weak and balancing the tree potential.

Different kinds and varieties of fruit trees have different advantages. Among deciduous fruit trees in northern China, the top advantage of pear tree is stronger than that of apple tree. When pruning, if the top advantage of pear tree is suppressed or improperly used, or it is difficult to distinguish it from apple tree, it will lead to abnormal phenomena such as vigorous growth, strong upper part and weak lower part, and delayed fruit bearing.

The top advantages of different varieties of apple trees are different: the top advantages of golden crown varieties are stronger than Guoguang, and Guoguang is stronger than ruby. Therefore, when cultivating fruiting branches and maintaining pruning, measures such as weak branch guidance or pruning should be taken to control its top advantage; For the pruning of the leading branches of Guoguang fruiting branch group, it is advisable to adopt pruning methods such as straight hair and avoiding rotation to maintain the top advantage. The strength of branches varies with the age of trees, and the strength of top dominance is also different. The top advantage of young trees and flourishing trees is stronger than that of old trees and weak trees; The tip advantage of upright branches is stronger than that of oblique branches and drooping branches; Full-cut buds of stout branches have a strong advantage at the top of branches.

The phenomenon of top advantage can be seen everywhere in production, and it is also widely used in shaping and pruning. If we master the reaction law of top advantage, we can skillfully control or use top advantage and do a good job in shaping or pruning fruit trees.