Lichens are important pioneer organisms which life is limited by water availability in polar terrestrial ecosystems. In this study, we investigated photosynthetic responses to the water and light of five lichen species that has different substrate selection and morphological feature on the field and laboratory.

Photosynthetic activity and water content of fruticose lichens were increased under the weak light condition on early morning of drying period. In contrast, water content of crustose lichen (Ochrolechia frigida) did not vary during a day of drying period, and photosynthetic activity increased along with solar radiation in daytime. Light response curve of photosynthesis of thallus and isolated photobiont of O.frigida did not, but fruticose lichen species showed strong photo-inhibition. In addition, lichen thallus of all species gained more water from air than their isolated photobiont under same humidity, and they showed higher photosynthetic activity than those of their photobionts.

Our results suggested that water condition of substrate and morphological features affected to the water content in lichen thallus. Then those differences make variation of the active photosynthetic period of each lichens and their photobionts studied.