Pruning removes leaves and buds that would develop into leaves.  Two apparently opposite effects occur from pruning young plants or those that do not have a heavy flower and fruit load.

Invigoration is the universal response to pruning.  Pruning leaf areas and buds that would be leaves allow the root system (which is not immediately affected) to supply each remaining leaf and bud with more water and nutrients than previously.  Individual shoot growth is stimulated, and these grow more rapidly and later into the season.  Leaves grow larger and are greener in color.  Even with larger leaves, total leaf area will be less on more severely pruned trees since there will be fewer shoots.  The leaf area of a pruned tree will transpire less water than that of an unpruned tree.

Dwarfing results from pruning or young plants and those that do not have a heavy flower and fruit load.  Pruning actually removes part of the plant, resulting in fewer leaves, or buds to develop into leaves.

Even though individual leaves on a pruned tree may be larger, total leaf area will be smaller than if the tree had not been pruned.  Shoots of pruned trees grow later in the season, using for their growth foods produced by the leaves.  A pruned plant has less time after shoot growth stops to use the food produced by leaves for the rest of the plant's growth and for storage or reserves for the next season.  Less total growth will result.  This can be easily observed or measured by the relative size of the trucks of trees that have been pruned more severely than others.

For a young plant at the end of the growing season following pruning, the following usually is the case: 1) top and root systems are in balance; 2) top and roots will be smaller than if the tree had not been pruned; 3) there will be less stored food in the pruned plants since these will have a smaller total leaf area and a shorter time for the leaves to be active between cessation of shoot elongation and the onset of rest or dormancy.

Invigoration and dwarfing effects depend upon how severely you prune.  Removing dead, weak, and heavily shaded branches has little effect while removing a like amount of healthy, well-exposed branches has a much greater influence.

Mature plants expected to set a heavy flower and fruit crop may become more vigorous without dwarfing.  Pruning off a number of flower buds leaves a fixed number of flowers to develop into fruit.  Remaining leaf buds have more food available for the shoots which will be more vigorous and have a greater leaf area per fruit than those of unpruned trees.

To subdue a tree or branch within a tree, prune more severely to reduce the total growth of a branch relative to another which is pruned only lightly or not at all.

To encourage a branch, prune it lightly or not at all.  Prune other branches severely, particularly those that shade or compete with the branch you wish to encourage.