Photosynthetic patterns of Cetraria cucullata (Bell.) Ach. at Anaktuvuk Pass, Alaska.

The daily photosynthetic patterns of Cetraria cucullata were followed over the 1976 summer period at Anaktuvuk Pass, Alaska. With the exception of rainy peroids, the lichen exhibited a strong diurnal pattern with peak photosynthetic activity occurring between 0300 and 0700 h. This correllated with periods of maximal lichen water retention and the presence of direct solar radiation. When the lichen was moist, a strong gradient in photosynthetic activity was observed with no activity in the lichen bases and maximal activity in the lichen tips.