title: Water availability modifies tolerance to photo-oxidative pollutants in transplants of the lichen Flavoparmelia caperata.
abstract: The hypothesis that a daily water supply allows a lichen to endure the negative effects of environmental concentrations of NO(x) and O(3) was tested with a transplant experiment. Five groups (0, A-D) of Flavoparmelia caperata samples derived from the same thalli were used for destructive, pre-exposure measurements (0), or exposed for 5 weeks in the rural collection site (A), and in a urban site with high levels of NO(x) and O(3) (B-D). Two groups (C, D) were daily watered half an hour before the daily peak of NO(x) (C), and O(3) (D). The comparison between pre- and post-exposure measurements of stress biomarkers revealed that the different thallus hydration regime modified the pollution tolerance as well as the physiology of the exposed samples. The non-watered group B suffered an evident decrease in F(v)/F(m) and reduced glutathione, but increased ion leakage, whereas the watered groups C and D showed only decreased non-photosynthetic-quenching, possibly derived from NO(x) exposure. Ozone, which was higher in the rural than in the urban site, did not significantly affect the lichen metabolism. Our results re-open the discussion on the so-called "drought hypothesis", which suggests that the lichen desert observed in urban areas of central and eastern Europe is more a matter of dry microclimate than of air pollution.
authors.affiliation: Dipartimento di Scienze della Vita, Università degli Studi di Trieste, via L. Giorgieri, 10, 34127, Trieste, Italy. tretiach@units.it
authors.forename: Mauro
authors.initials: M
authors.lastname: Tretiach
authors.forename: Silvia
authors.initials: S
authors.lastname: Pavanetto
authors.forename: Elena
authors.initials: E
authors.lastname: Pittao
authors.forename: Luigi
authors.initials: L
authors.lastname: Sanità di Toppi
authors.forename: Massimo
authors.initials: M
authors.lastname: Piccotto
mesh_terms: D002980:Climate; D004785:Environmental Pollutants / Q000494:pharmacology*; D008011:Lichens / Q000187:drug effects / Q000502:physiology*; D009589:Nitrogen Oxides / Q000494:pharmacology*; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010126:Ozone / Q000494:pharmacology*; D010788:Photosynthesis; D014867:Water / Q000378:metabolism*
chemical_list: D004785:Environmental Pollutants; D009589:Nitrogen Oxides; D014867:Water; D010126:Ozone