
Originally Posted by
raybark
Alan Koch, who does a lot of breeding, once told me that, with flowers of wildly disparate size, often, the pollen of the smaller flower will not grow pollen tubes sufficiently long to reach the ovary.
I was of the impression that the phenomenon was a direct, genetic effect, sort-of like short parent typically having short kids. However, apparently some of that is simply a case of running out of resources to keep growing at a sustained rate. Some recent studies have shown that Kelpak (sold as KelpMax in North America) stimulates pollen tube growth, so maybe applying it to plants at the time of pollination (or a little before?) might help with that.