Surface hydrophobicity causes SO2 tolerance in lichens

Markus Hauck, Sascha-Rene Juergens, Martin Brinkmann, Stephan Herminghaus

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46 Citations (Scopus)

Abstract

Background and Aims
The superhydrophobicity of the thallus surface in one of the most SO2-tolerant lichen species, Lecanora conizaeoides, suggests that surface hydrophobicity could be a general feature of lichen symbioses controlling their tolerance to SO2. The study described here tests this hypothesis.

Methods
Water droplets of the size of a raindrop were placed on the surface of air-dry thalli in 50 lichen species of known SO2 tolerance and contact angles were measured to quantify hydrophobicity.

Key Results
The wettability of lichen thalli ranges from strongly hydrophobic to strongly hydrophilic. SO2 tolerance of the studied lichen species increased with increasing hydrophobicity of the thallus surface. Extraction of extracellular lichen secondary metabolites with acetone reduced, but did not abolish the hydrophobicity of lichen thalli.

Conclusions
Surface hydrophobicity is the main factor controlling SO2 tolerance in lichens. It presumably originally evolved as an adaptation to wet habitats preventing the depression of net photosynthesis due to supersaturation of the thallus with water. Hydrophilicity of lichen thalli is an adaptation to dry or humid, but not directly rain-exposed habitats. The crucial role of surface hydrophobicity in SO2 also explains why many markedly SO2-tolerant species are additionally tolerant to other (chemically unrelated) toxic substances including heavy metals.
Original languageEnglish
Pages (from-to)531-539
JournalAnnals of Botany
Volume101
Issue number4
Early online date12 Dec 2007
DOIs
Publication statusPublished - Mar 2008
Externally publishedYes

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