The photosynthetic performance (photosynthesis response curves to light and water content at various temperatures) of the pale and dark forms of the lichen Usnea spacelata from Cape Royds

Individuals of the Usnea sp were identified and collected and their distribution recorded at Cape Royds. Two forms, a pale shade form and a dark sun form were identified.

Specimens were removed and used for gas-exchange studies. Full photosynthetic response curves to light were obtained for the dark and pale forms at 10, 5, 0, -5 and -10°C. A photosynthesis to thallus water content curve was also produced for both dark and pale forms.