The resistance of the moss Polytrichum commune to acute exposure of simulated acid rain or ozone compared to two fern species: Spore germination

This study was done I) to determine the useful[ness of spore germination of selected non-seed plants as a bioassay for simulated acid rain (SAR) and O -3 effects and 2) to compare the results of spore germination with Seed pla nt pollen exposure studies. Three taxa of common and wide occurrence in eas tern North America were employed-the moss Polytrichum commune and two ferns , Athyrium felix-femina and Onoclea sensibilis. In two separate experiments , spores of the three taxa were exposed to simulated acid rain solutions (S AR) ranging from pH 2-7 and to four concentrations of ozone (O-3) (11, 50, 100, and 150 ppb) to assess effects on spore germination. After exposure to SAR, P. commune spore germination was inhibited only at pH 2 (0%). Germina tion was 100% at all other pH levels. Spore germination for both fern speci es was approximately 100% at pH 4 and higher, 6-20% at pH 3, and 0% at pH 2 . Exposure to O-3 had no effect on P. commune spore germination, which rema ined 100% at all four concentrations. Athyrium felix-femina spore germinati on decreased with increasing O-3 concentration At 150 ppb O-3 A. felix-femi na germination decreased 50%, compared with germination at ambient levels ( II ppb). Onoclea sensibilis spore germination increased 15% in 100 ppb O-3- air compared with germination in ambient air (II ppb) suggesting a possible tonic effect. However, O. sensibilis germination decreased 66% as the O-3 concentration increased to 150 ppb, compared with germination in ambient ai r. These findings demonstrate that P. commune spore germination is resistan t to the short term exposure to both acid rain and O-3, while the two fern taxa appear to be sensitive to these two pollutants.