title: Uptake and localization of gaseous phenol and p-cresol in plant leaves.
abstract: Understanding foliar uptake processes for organic air pollutants is critical to predicting the fate of these compounds, including their entry into the food chain and their susceptibility to plant-, microbe-, and light-mediated degradation. We characterized the uptake kinetics for gaseous phenol and p-cresol into the leaves of maize seedlings in a closed system over periods up to 23h. When leaves were exposed to mixtures of phenol and p-cresol (3-50microg l(-1) each), the air concentrations of the compounds rapidly decreased, showing residence times of 4-6h. The stomata of the leaves were mostly or completely closed, suggesting that uptake was primarily through the cuticle. The involvement of a cuticular uptake pathway was confirmed based on increased uptake into two cuticular mutants of maize. Models of the uptake data suggested that, at the concentrations used, phenol and p-cresol were taken up in a biphasic manner, consistent with previous two-compartment models for foliar uptake of lipophilic compounds via a cuticular pathway. These models also indicated that phenol was taken up at a slightly faster rate than p-cresol. To begin to understand the fate of these compounds, we examined the location of (14)C in leaves exposed to (14)C-phenol. Significantly more (14)C accumulated in the terminal centimeter than in the central and basal regions of the leaves on both a mass and area basis. This is the first demonstration that a gaseous organic compound, or its breakdown products, accumulates in a spatially non-uniform manner in leaves following foliar uptake. These findings support a role for plants as natural, or deliberate, attenuators of airborne pollutants, and suggest potential availability of these compounds to the leaf surface microflora.
authors.affiliation: Department of Plant Pathology, Iowa State University, 207 Science I, Ames, IA 50011-3211, United States. gbeattie@iastate.edu
authors.forename: Gwyn A
authors.initials: GA
authors.lastname: Beattie
authors.forename: Janice R
authors.initials: JR
authors.lastname: Seibel
mesh_terms: D000393:Air Pollutants / Q000378:metabolism; D003408:Cresols / Q000378:metabolism*; D005740:Gases / Q000378:metabolism*; D019800:Phenol / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism*; D036226:Seedlings / Q000378:metabolism; D003313:Zea mays / Q000378:metabolism*
chemical_list: D000393:Air Pollutants; D003408:Cresols; D005740:Gases; C032538:4-cresol; D019800:Phenol