The plant growth hormone which helps in enlarging the grape fruit is

The plant growth hormone which helps in enlarging the grapefruit is Gibberellic acid. In grapes, gibberellins are produced in the developing embryos and cause the berries to enlarge.
Gibberellic acid is a synthetic plant growth regulator. It is often used to obtain enlarged table grape berries and induce seedlessness in them. However, the effects of GA₃ on rachis elongation and bunch compactness in wine-grape production.