Surface Hydrophobicity Causes
SO2 Tolerance in Lichens
Hauck et. all
Presented by:
Sarah Laperriere
Ari Nalbandian
Purpose
Does surface
hydrophobicity cause
sulfur dioxide resistance?
Key Words
 Hydrophobic (water-fearing)
 Repels water
 Hydrophilic (water-loving)
 Attracted to water
 Contact Angle
Markus Hauck
 Georg-August University of Göttingen
 Interests include:
 Lichen secondary metabolites
 Biodiversity
 Global change ecology
 Long walks on the beach
http://www.goettingen.studip.de/extern.php?module=Persondetails&config_id=91362d34fe8a
e37349a29787e7d&range_id=2b648cb9a0cf4573c5d4c3d661e6d1df&username=mhauck
Sulfur Dioxide (SO2)
http://volcanoes.usgs.gov/Imgs/Jpg/GasEffects/GasesChemistry.jpg
Why Be Hydrophobic?
 Thallus saturated with water = less gas exchange = less
photosynthesis
 Hydrophobic thallus exterior prevents thallus from
becoming saturated
http://www.buffelskloof.info/images/Lichen%20detail.JPG
Variables
 Independent - Lichen SO2 tolerance
 Dependent - Lichen hydrophobicity
Experimental Design
 50 lichen species, known low to high SO2 sensitivities
 500 m deionized water droplets placed on surface of
air-dry thalli
 Contact angles measured to quantify hydrophobicity
 Replicated 5 times
 Lichens extracted with acetone to remove extracellular
substances
Methods of Tabulation and
Evaluation
Contact Angle
http://www.dsm.com/en_US/html/dep/adhesive_bonding.htm
Results
Table 2: contact angles of water droplet placed on
the thallus surface of lichen species
 http://aob.oxfordjournals.org/content/101/4/531/T2.ex
pansion.html
Water droplets placed on the surface of lichen thalli of Bacidina inundata (A), Cetraria
islandica (B), Cladonia coniocraea, podetium (C), C.
Hauck M et al. Ann Bot 2008;101:531-539
© The Author 2007. Published by Oxford University Press on behalf of the Annals of Botany
Company. All rights reserved. For Permissions, please email:
journals.permissions@oxfordjournals.org
Data Interpretation
 “Increasing SO2 tolerance with increasing
hydrophobicity of the thallus surface in a set of 50
lichen species suggests that SO2 tolerance in lichens
primarily depends on the ability to reduce uptake of
acidic precipitation containing SO2 and its derivatives
formed in aqueous solution.”
Contact angles of water droplets placed on the surface of lichens of different SO2 tolerance
(A) or growth form (B).
Hauck M et al. Ann Bot 2008;101:531-539
© The Author 2007. Published by Oxford University Press on behalf of the Annals of Botany
Company. All rights reserved. For Permissions, please email:
journals.permissions@oxfordjournals.org
Strengths & Weaknesses
 Strengths
 Data significance, clarity
 Discusses buffering capacity of substratum
 Discusses characteristics of hydrophilic lichen
 Weaknesses
 Do not discuss role of systematic position, thallus
morphology, or photobiont choice
 Do not discuss hydrophobic substances on thallus
 Sensitivities of some species still lacking