Breeding System and Pollination Levels of Banksia ericifolia

Experiments were carefully designed to determine the breeding system of Banksia ericifolia L.f. An equivalent percentage of flowers (78%) contained pollen tubes following self-pollination and open-pollination while a significantly smaller percentage of flowers in an autogamy treatment (44%) and cross-pollination treatment (55%) contained pollen tubes. Significantly more of the inflorescences in the open-pollination (60%) and cross-pollination (33%) treatments produced fruit compared with those in the self-pollination (11%) and autogamy treatments (13%). We suggest that B. ericifolia is largely self-incompatible because fruit production did not reflect pollen tube abundances. The influence of pollination levels on fruit production was determined by reducing the number of flowers on an inflorescence to 100 (i.e. 10% of original) or fewer and hand-pollinating these with cross pollen. There was no difference in fruit production between inflorescences with reduced flower number and open-pollinated inflorescences which had their full complement of flowers. Thus, the ability of an inflorescence to produce fruit appears more likely to be determined by the type of pollen received (cross versus self) rather than by the number of pollinated flowers it contains.