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Photosynthetic performance of Xanthoria mawsonii C. W. Dodge in coastal habitats, Ross Sea region, continental Antarctica

Published online by Cambridge University Press:  19 December 2005

Stefan PANNEWITZ
Affiliation:
Botanisches Institut, Christian-Albrechts-Universität Kiel, Olshausenstr. 40, 24098 Kiel, Germany
T. G. Allan GREEN
Affiliation:
Biological Sciences, University of Waikato, Private Bag 3105, Hamilton, New Zealand
Mark SCHLENSOG
Affiliation:
Botanisches Institut, Christian-Albrechts-Universität Kiel, Olshausenstr. 40, 24098 Kiel, Germany
Rod SEPPELT
Affiliation:
Australian Antarctic Programme, Channel Highway, Kingston 7050, Tasmania, Australia
Leopoldo G. SANCHO
Affiliation:
Dep. Biologia Vegetal II, Fac. De Farmacia, Universidad Complutense, 28040 Madrid, Spain
B. SCHROETER
Affiliation:
Botanisches Institut, Christian-Albrechts-Universität Kiel, Olshausenstr. 40, 24098 Kiel, Germany

Abstract

Xanthoria mawsonii C. W. Dodge was found to perform well physiologically in a variety of habitats at high latitudes in continental Antarctica. The net photosynthetic rate of 7·5 μ mol CO2 kg−1 s−1 is exceptionally high for Antarctic lichens. Field and laboratory measurements proved the photosynthetic apparatus to be highly adapted to strong irradiance. The cold resistance of the photosystem II reaction centres is higher than the photosynthetic CO2 fixation process. Optimum temperature for net photosynthesis was c. 10°C. The lichen grows along water channels where it is frequently inundated and hydrated to maximum water content, although net photosynthesis is strongly depressed by super saturation. In these habitats the lichen is photosynthetically active for long periods of time. Xanthoria mawsonii also grows at sites where it depends entirely on the early spring snow melt and occasional snow fall for moisture. It has an exceptionally short reactivation phase and is able to utilize snow immediately. Recovery of activity by absorbing water vapour from air, though practically possible, seems to be of ecological importance only under snow at subzero temperatures.

Type
Research Article
Copyright
© British Lichen Society 2005

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