|Cane, James - Jim|
Submitted to: American Journal of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/23/2003
Publication Date: 10/20/2003
Citation: Cane, J.H., Schiffhauer, D. 2003. Dose-response relationships between pollination and fruiting refine pollinator comparisions for cranberry (Vaccinium macrocarpon ait.). American Journal of Botany. 90:1425-1432 Interpretive Summary: Like many fruit crops and wildflowers, cranberries need pollinators. Bee species are shown to differ in the amount of pollen delivered to cranberry stigmas, but how does it translate into fruit and seed production? Through manual pollinations with incremental doses of pollen, we developed predictive curvilinear relationships between stigmatic pollen loads and cranberry fruit set, fruit size and seed count. Transformation of raw pollen loads by these reproductive response equations yielded more meaningful predictions for differences in pollination efficacies among cranberry bees. Shortcuts are suggested to extend these calculations to other cropping and wildland flowering plants.
Technical Abstract: Comparisons of pollinator efficacy using pollen received on stigmas can be refined by incorporating experimental dose-response relationships for pollen deposition and fruiting responses. A range of discrete pollen doses that were applied to cranberry stigmas resulted in decelerating curvilinear responses for fruiting, berry size, and seed set. Minimum thresholds and maximum asymptotes bounded reproductive responses to incremental stigmatic pollen loads. Four bee species were compared for their pollination efficacies at commercial cranberries, using counts of pollen received by stigmas during single bee visits to previously virgin flowers. Differences between these bee species were found to be exaggerated when raw pollen counts were used for comparison because foragers of some species often delivered pollen in excess of that needed to maximize fruit and seed production. Six-fold differences between species in mean pollen deposition translated into 1.5-2-fold differences in predicted cranberry fruit set and size. Implications for pollen tube competition and agricultural production are discussed.