Ecophysiology of lichens in the dry valleys of Southern Victoria Land, Antarctica

Abstract

CO2 exchange was measured in three cryptoendolithic lichen samples from the ice-free mountains of Southern Victoria Land. Optimum temperature for net photosynthesis at different light intensities ranged from below 2°C to about 7°C; the upper compensation point ranged from 5°C to 15.7°C, and the lower compensation point could be estimated in two samples as being between-6°C and-8°C. Dark respiration rates were higher than those of net photosynthesis. The results indicate that these cryptoendolithic lichens are not more adapted to low temperatures than are crustose lichens from coastal Antarctica. Calculations show that optimum temperatures for photosynthesis may not be reached in the natural environment. Photosynthetic rates were low, but they increased when samples were split into smaller pieces, permitting gas exchange through broken rock surfaces. In nature, when gas exchange is possible only through the intact rock crust, these apparent rates are probably even lower.