① During the fruit set stage of grapes, GA3 can increase the levels of gibberellins and auxins in young fruits, prevent the formation of abscission layers, and attract nutrients to the young fruits, thereby improving fruit set rate. The recommended concentration typically ranges from 12.5 to 100 mg/L.
② Spraying or dipping the clusters of certain grape varieties from full bloom to within 5 days after petal fall significantly increases berry size. This is primarily achieved by promoting cell division, especially in the apical meristem, leading to elongation and enlargement of pulp cells.
③ Breaking seed dormancy: Dormant grape seeds can be forced to germinate by soaking them in a high concentration (8,000 mg/L) of GA3 for approximately 20 hours.
④ For some wine grape and seedless grape varieties with overly compact clusters, applying 1–5 mg/L GA3 to inflorescences before flowering, or 10–15 mg/L GA3 during flowering, can elongate the rachis and reduce fruit set, thereby achieving cluster loosening.
⑤ Increasing rootstock shoot yield: For grape rootstock varieties with weak growth and short internodes, as well as mother vines used for cutting propagation, repeatedly spraying low-concentration GA3 solution during the growing season can promote vine growth, elongate internodes, increase shoot yield, and improve cutting utilization efficiency.
