According to Biology Online, gibberellins promote the growth in the seed's embryo. Gibberellins can be created by using the fermentations which are produced by the mold Gibberella fujikuroi. Commercial growers have found that using gibberellins will increase the yield of their fruit trees.
Gibberellins and Seedless Grapes
Growers use gibberellins to increase the size and yields of their seedless grapes. Since these grapes don't have seeds, they aren't able to produce gibberellins naturally. Growers have found that by spraying the grapes with gibberellins, they are able to produce large, full bunches of grapes that are similar in size to seeded grapes. Not only are the seedless grapes larger, the gibberellins increases the size of the rachis, the "branches" on which the grapes grow, which can make the bunches of grapes larger, reducing the risk of mold between the grapes.
Gibberellins and Apples
In many cases, apple varieties include some apples that grow every other year. Growers have found that by spraying the trees in the "off" year with gibberellins, they can cause flowers to form, and thereby fruit, even during these years.
Gibberrellens and Pears
In Europe, some growers use gibberellens to promote the growth of pears even in growing seasons plagued by inclement weather. By spraying the pear trees (and in some cases apple trees) with gibberellens, the growers are able to produce seedless fruit.
Gibbellens and Citrus
Citrus growers like gibberellens as well. For oranges and also tangerines, gibberellens can slow down the aging rate of the rinds. For lemons and limes, gibberellens can make these fruits larger.
Gibberellens and Sugarcane
Sugarcane is a plant that flourishes in warmer climes. In order to encourage it to grow in cooler climates, growers have found that the application of gibberellens can induce it to produce more.