CARBON ACQUISITION AND WATER RELATIONS OF LICHENS IN POLAR-REGIONS - POTENTIALS AND LIMITATIONS

Primary production in lichens, as in all plants, is the result of gain s and losses. Losses of carbon may be high under extreme environmental conditions. In the harsh climate of polar regions lichens use much ca rbon for maintenance and in their stress response. Thallus biomass is preserved through periods of darkness, extremely low temperatures and snow cover. On the other hand, lichens are photosynthetically active a t temperatures below 0 degrees C. They can make use of melted water fr om snow and ice and take up water vapour from snow. Physiological adap tations and environmental conditions under which growth is possible ar e discussed in terms of our recent results. A concept model describes the main parameters that influence carbon acquisition, growth and wate r relations of lichens in polar regions. (C) 1995 The British Lichen S ociety