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Tretiach, M./ S. Pavanetto/ E. Pittao/ L. S. Di Toppi/ M. Piccotto 2012: Water availability modifies tolerance to photo-oxidative pollutants in transplants of the lichen Flavoparmelia caperata. - Oecologia 168(2): 589-599. [RLL List # 226 / Rec.# 33717]
Keywords: Drought hypothesis/ Hydration/ NOx/ O3/ Pollution/ Transplant
Abstract: The hypothesis that a daily water supply allows a lichen to endure the negative effects of environmental concentrations of NOx and O3 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 NOx and O3 (B-D). Two groups (C, D) were daily watered half an hour before the daily peak of NOx (C), and O3 (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 Fv/Fm and reduced glutathione, but increased ion leakage, whereas the watered groups C and D showed only decreased non-photosynthetic-quenching, possibly derived from NOx 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. © 2011 Springer-Verlag.
URL: http://dx.doi.org/10.1007/s00442-011-2104-z
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