Inhibition of Cladonia cristatella and Sordaria fimicola Ascospore Germination by Lichen Acids

Abstract

Germination responses of Sordaria fimicola and Cladonia cristatella ascospores were observed in the presence of three pure lichen acids on buffered media ranging in pH from 4 to 7. Acetone solutions of either vulpinic (VUL), evernic (EVE) or stictic (STC) acid were poured onto buffered agar at a concen- tration of 2.7 x 10-3 M and the acetone allowed to evaporate. Ascospores were deposited on the agar surface and the percent spore germination was recorded after 24 hr. Comparisons were made with control plates to which only acetone was added. Cladonia cristatella spore germination was slightly but significantly inhib- ited by VUL, but no inhibitory effects were observed for EVE or STC. Sordaria fimicola spores were severely inhibited by both VUL and EVE, but not STC. No pH effects on lichen compound toxicity were observed, but C. cristatella spores exhibited little germination at pH 7. Lichen acids appear to be capable of func- tioning as allelopathic agents in nature; however, lichenized fungi may be better able to tolerate the inhibitory effects of lichen acids than nonlichenized fungi. Lichen secondary compounds are known to inhibit or delay germination of gymno-