Alternative outcomes of natural and experimental high pollen loads

Seed production is assumed to be a positive monotonic function of pollen deposition and/or pollinator visitation, ie there would be only two outcomes of excess pollen levels: an increase in fruit or seed set, or no increase. However, a substantial minority of the studies reviewed here has found that seed production declines with increased pollen loads. Explanations may include pollen tube crowding, pollen removal or stigma damage by pollen thieves or pollinators, stigma damage during hand-pollination, application of low-diversity or local pollen, effects of bagging flowers, missed stigma receptivity, and the application of inviable pollen. -from Authors