Chapter 5 Negative vs. Positive Functional Plant Responses to Air Pollution: A Study Establishing Cause–Effect Relationships of SO2 and H2S

Throughout the world, natural and agro-ecosystems are at risk from sulfurous air pollutants. However, establishing cause-effect relationships for these air pollutants, and determining acceptable atmospheric concentrations of them, are complicated by their paradoxical effects on plant functioning. Sulfurous air pollutants can act as both toxin and nutrient for plants. However, it is unclear to what extent metabolism contributes to the detoxification of absorbed sulfur gases, as there is no clear-cut transition in the level or rate of metabolism of the absorbed sulfur gases and their phytotoxicity. Moreover, the effects of sulfurous air pollutants on plant functioning are most probably strongly dependent on the sulfur status of the soil.