CONTRASTING GROWTH-RESPONSES OF HERBACEOUS SPECIES TO ACIDIC FOGS

Plants of Lolium perenne L., Holcus lanatus L., Lotus corniculatus L. and Anthoxanthum odoratum L. were exposed to fog treatments at pH valu es of 2.5, 3.5, 4.5 and 5.6. There were three 4-h exposures per week p roviding a total of 6 mm deposition. Supplementary watering with pH 4. 5 simulated acid rain provided a further 24 mm deposition per week. Pl ants of Lotus corniculatus showed reduced growth at pH 2.5 and 3.5 com pared with the less acidic fog treatments and greatest dry matter accu mulation at pH 4.5. In contrast, plants of the other three species sho wed greater dry weights in the most acidic pH 2.5 treatment in compari son with other treatments. For H. lanatus and A. odoratum, the increas ed dry matter production at pH 2.5 was associated with a reduced root/ shoot ratio. There was a promotion of flowering stem production in the pH 2.5 treatment for Lolium perenne and increased numbers of flowers and buds in the pH 5.6 treatment for Lotus corniculatus. It is suggest ed that leguminous species are more susceptible to acid deposition tha n other plant families.