ANTIFUNGAL ACTIVITY OF RIPE ERICACEOUS FRUITS - PHENOLIC-ACID INTERACTIONS AND PALATABILITY FOR DISPERSERS

Chemical characteristics of antifungal extracts of ripe fruit pulp of six ericaceous plants that differ in fruit ripening phenology and other dispersal characteristics were examined. The antifungal activity of these fruits is particularly interesting because of contrasting effects of pulp secondary chemistry upon birds that disperse the seeds. Whereas extracts of summer-ripening fruit do not affect (or affect positively) the feeding rates of birds feeding on artificial-pulp media, extracts of fall-ripening fruit are very much a deterrent Results of fungal growth tests indicate that synergistic interactions of small phenolic constituents with small organic acids were most likely sources of antifungal activity for all but one species (Arctostaphylos uva-ursi), for which astringent polyphenolics and steroidal saponins were implicated. Fall-ripening fruit are apparently more of a deterrent to frugivores due to higher concentrations of organic acids in interaction with phenolic constituents, or higher concentrations of tannins and saponins. In conclusion, we stress the challenges that chemical synergism may present to chemical ecologists, and the importance of interactive effects of "primary" chemicals in plant defense.