Gibberellin plays a crucial role in the development of seedless grapes by manipulating the natural processes of fruit formation. Here's how gibberellin influences the development of seedless grapes:
Induce Parthenocarpy
Gibberellin can induce parthenocarpy, a phenomenon where fruits develop without fertilization. This is achieved by mimicking the hormonal changes that occur after successful pollination, triggering the fruit to develop as if seeds were present.
Inhibit Seed Formation
Applied at specific stages of flower development, typically 7-14 days before full bloom, gibberellin can inhibit pollination and fertilization, effectively preventing seed formation.
Promote Early Growth
By promoting early cell division and elongation, gibberellin contributes to the rapid expansion of the fruit's size. This is particularly important for seedless grapes, which often have smaller berries due to the lack of endogenous hormones that promote fruit set and growth.
Enhance Nutrient Absorption
Gibberellin can increase the content of auxin, a plant hormone that aids in nutrient uptake. This effect helps young seedless grape berries to absorb more nutrients, leading to increased size and improved fruit quality.
Time and Application
The timing of gibberellin application is critical. Applying it too early or too late can result in the development of seeded grapes. Optimal application windows, such as 10-16 days before full flowering for seedless varieties, can lead to a high rate of seedless fruit formation, sometimes exceeding 98-99%.
Specific Varietal Responses
Different grape varieties respond differently to gibberellin treatments. For example, Kyoho grapes treated with gibberellin 4-6 days before the first flowering and 10 days before full bloom can result in over 95% of the grapes becoming seedless.
Cellular and Physiological Changes
Gibberellin promotes the division of cells and the elongation of cell walls, directly influencing the physical growth of the fruit. It also affects the transport and accumulation of nutrients within the fruit, further enhancing its development.
By carefully managing the application of gibberellin, growers can significantly increase the production of seedless grapes, which are highly sought after for their convenience and eating quality. The precise timing and method of application are key to achieving the desired results without compromising the overall health and productivity of the grapevines.