The impact of in vitro ozone and sulfur dioxide fumigation on pollen from two Fraser fir populations was examined. Populations were located at Mt. Rogers, Va, and Mt. Mitchell, S.C.. Two age groups "young" (less then 30 years old) and "old" (more then 40 years old) were examined within each population. No statistically significant age group differences in pollen germination percentage or pollen tube length were found. Mt. Mitchell pollen had a higher germination percentage than Mt. Rogers population. The statistically significant differences in pollen germination between populations were most probably due to the confounding effect of collection practices, and environmental conditions during 1986 pollen collection, rather than actual differences between populations. In vitro pollen fumigation with sulfur dioxide had no impact on pollen germination while fumigation with ozone decreased pollen germination percentage but did not change pollen tube length. Most of the variation in pollen germination percentage, and pollen tube length was due to genotype of the pollen parent tree. The phenotypic expression of six isozymes (previously correlated with resistance to air pollutants) in pollen was studied using polyacrylamide gel electrophoresis. The pattern of isozyme distribution among pollen phenotypes confirmed results from pollen germination studies. There was a difference between locations but no difference between age groups. None of isozyme phenotypes was correlated with a "resistance" to pollen fumigation with ozone or sulfur dioxide. / Master of Science