How to achieve optimal fruit set?

• Written by Paul Hills

The Effective Pollination Period (EPP) is the window of time during which a flower can be successfully fertilized. It corresponds to the interval in which the ovule remains viable and the pollen tube reaches the embryo sac before the ovule deteriorates. If the pollen tube does not arrive in time, fertilization does not occur and, as a result, the fruit either fails to form or later drops.

The three processes that determine the EPP are: (i) stigma receptivity, (ii) pollen tube kinetics, and (iii) ovule development (Sanzol, 2001). In general, the pollen tube develops more slowly at low temperatures, which benefits ovule longevity. Conversely, high temperatures accelerate pollen tube growth but also hasten the degeneration of the stigma and ovule.

Ensuring optimal seed fertilization is particularly important in fruit species with naturally low fruit set and retention rates, and where abiotic stress factors can slow pollen tube growth and reduce the brief window of opportunity for fertilization.

In this context, numerous field and laboratory studies indicate that the use of biostimulants can enhance pollen germination and pollen tube elongation, promoting more effective fertilization and, consequently, improved fruit set and yield (Gupta et al., 2024). Kelpak® is a powerful biostimulant that increases pollen viability, boosts germination, and ultimately stimulates pollen tube elongation. The delicate balance and pristine molecular structure of its bioactive compounds, such as phlorotannins, polyamines, and brassinosteroids, make this biostimulant a key ally in achieving efficient fruit set and retention.