The crown of fruit trees expands with the growth of tree age, and there are too many branches and leaves, which will inevitably lead to the consequences of dense outside and empty inside, premature aging of trees, serious years and low fruit yield and quality. Timely and reasonable pruning can play the following roles:

① Adjust the rational distribution of branches and leaves. That is, on the basis of reshaping, the density, distribution direction and leaf area coefficient of each part of the crown are adjusted to maximize the effective photosynthetic area of the crown.

② Regulating growth and fruiting. Make nutrition grow normally but not too much; Moderate flowering and fruiting without weakening the tree; At the same time, it can prevent fruit trees from aging ahead of time and renew and rejuvenate in time.

③ Adjust the proportion of branches. Short branches have short growth period, low consumption and early accumulation, but few leaves and low total photosynthesis; Vegetative branches have a long growth period and high consumption, but they also accumulate a lot in the later stage. Different tree species and tree ages need to have corresponding and appropriate branch proportions, so that the operation, distribution, consumption and accumulation of nutrients in a year's growth cycle can be coordinated according to the normal growth and reproduction rhythm. This can be achieved by pruning.

(4) Pruning can also balance the growth potential among the population plants and between the main branches of the plants, so as to achieve a balanced yield and facilitate management. In addition, pruning is also a means to coordinate the growth of shoot and root system.

The regulation of pruning on the growth and development of branches, leaves and fruits is related to the change of apical dominance. Because the transport direction of cytokinin produced by roots is opposite to the direction of gravity, the more upright the branches are, the higher the position of buds is, and the more they get, so the faster the cells divide, the more prosperous they grow. However, the germination and growth of the lower bud of the terminal bud were inhibited. Once the branch is cut off, the top advantage is transferred to the cutting bud, and the growth potential of each bud under it is weakened in turn, so that it cannot germinate into a hidden bud, thus changing the original germination rate and branching ability, and making the branch analogy and the growth potential of vegetative branches also change. In addition, the development and quality of buds on branches are also different, which is called bud heterogeneity. Generally speaking, the quality of buds is closely related to the size and function of leaves on nodes, the time of bud formation, the overall nutritional status of trees and environmental factors. Therefore, pruning also takes advantage of the heterogeneity of buds, and plays its regulatory role by choosing appropriate pruning buds. But pruning with similar branches and cut parts can not achieve the same effect. This is because different tree species and varieties have different germination and branching habits. Usually, the varieties with stout branches grow vigorously and bloom later than the varieties with high germination rate. Different tree species and varieties have different fruiting habits. In order to get the expected effect of pruning, it is necessary to know this in advance.