Young holly plants were exposed for up to 9 months to simulated acid fog at a chemical composition, pH range and deposition pattern consistent with those reported for an elevated site in northwest England. Plants were exposed to acid fog at pH 5.6 (control), pH 4.5, pH 3.5 and pH 2.5. Water permeability was higher in enzyme-isolated cuticles from low-pH leaves. Foliar leaching amounts of Mg2+, Ca2+ were higher in leaves exposed to lower pH acid fog. Similar effects for K+ leaching rates were not significant. Increases in cuticular permeability and cation leaching were not accompanied by any observable changes in surface structure, as revealed by studies with wettability and extractable wax. It is suggested that any changes in cuticular functioning were the result of alterations to the intracuticular rather than epicuticular structure.
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We are grateful for the valuable help provided by Leena Rapponen (AAS analysis), Phil Smith (transpiration chamber construction), Ray Rafarel and Sam Bell (acid fog facilities ). Acknowledgement is made of the valuable discussions with Professor T.A. Mansfield, Dr. K. Lendzian, Dr. G. Kerstiens and Dr. J. Wolfenden. Financial support for one author (MB) was provided by a NERC CASE award.