Abortion of Floral Buds in Acomastylis rossii Plants Exposed to Artificial Acid Mists in Alpine Tundra

Abstract

Plants of Acomastylis rossii were treated over a three-year period with artificial acid mists of pH 2.5, 3.5, or 4.5 prepared with sulfuric acid or nitric acid. Treatments were made in the field twice weekly for eight weeks during each of the three growing seasons. Significant decreases in the percentage of plants flowering were noted in each year of the study in plants treated with sulfuric acid mist at pH 2.5. Significant decreases in flowering with sulfuric acid at pH 3.5 and in leaf number with sulfuric acid at pH 2.5 and 3.5 occurred in the third year of treatments as well. Some individual plants flowered in one, two, or three of the years, indicating that new floral primordia were being produced during the treatment period. Plants that flowered produced viable, germinable seeds. No effects of nitric acid mists were noted during the study period. Treatments with citrate buffer solutions (pH 6.2) used to determine if the plants were responding to sulfate independently of pH showed no significant differences for any of the measurements taken. The observed decreases in flowering are apparently a sulfuric acid effect and are not attributable to hydrogen ions or sulfate ions independently of each other. Experiments with plants that had visible floral buds indicate that plants aborted the floral structures in response to direct contact of buds with solution from the acid mists. The growth form of the plants enhances contact by causing pooling of the solutions on top of the developing buds in pockets formed by the basal leaves.