Effects of Acidity on Tree Pollen Germination and Tube Growth

摘要

Most of the northeastern hardwood forests in North America are exposed repeatedly to acidic rainfall at pH values below 5.0. Pollen germination, tube growth and fertilization, important parts of the reproductive process, are sensitive to changes in their chemical environment. Accordingly, we investigated the effects of acidity on pollen germination and tube elongation of four northeastern tree species, flowering dogwood, black birch, yellow birch, and sugar maple. Pollen was collected and germinated in a growth medium that was acidified to pH values ranging from 5.0 to 2.6. Pollen was found to be sensitive to acidification of the germination medium to below pH 4.2. These results suggest that acidic rain that now occurs in eastern North America may influence reproductive processes that are necessary for seed set and regeneration in northern hardwood forests.