Field Measurements of Photosynthesis of Umbilicarious Lichens in Winter

Abstract

The photosynthetic performance of Lasallia pustulata and Umbilicaria spodochroa was measured both in the field on granitic rock in southern Norway and in the laboratory under controlled conditions of light and temperature. In the field thallus temperatures varied between − 2 and + 5 °C during the daylight period in January 1994. In situ water contents were between 50 and 400% d.wt. in L. pustulata and between 100 and 500% d.wt. in U. spodochroa. The lichens were active during the whole period of investigation. Photosynthetic rates reached 13.03 μmol CO2 g Chl−1 s−1 in L. pustulata and 5.56 μmol CO2 g Chl−1 s−1 in U. spodochroa. Ice formation on the thallus surface did not impede CO2 exchange. Light was mainly the limiting factor, as could be confirmed by the laboratory experiments. In general, habitat conditions never provided optimum photosynthetic rates but photosynthetic carbon balance was positive during 4 of the 5 days investigated. The coldest day was photosynthetically almost as efficient as the warmest day during this period.

Cryoproective role of ribitol in Xanthoparmelia somloensis

“…Towards subzero temperature, however, many lichen species perform gradually decreasing but still substantial photosynthesis. This has been reported in gasometric field studies done in cold regions (Kappen et al 1996).…”

Winter photosynthetic activity of twenty temperate semi-desert sand grassland species

“…Grasslands make up a large portion of the natural vegetation in the temperate continental climate. The winter photosynthesis of grassland plants (Adams et al, 2001;Barstow and Erbisch, 1977;Kappen et al, 1996;Nowak and Caldwell, 1984;Regehr and Bazzaz, 1976;Werk et al, 1983) is of great importance in view of the global climate change, since theoretically, these grasslands can act as a potential carbon sink in the cold winter period. In temperate climates during most of the cold period (late autumn, winter, early spring), the perennial plants overwintering with green photosynthetic tissues and leaves are regularly exposed (at least in early morning) to frost.…”

Intrathalline and size‐dependent patterns of activity in Lasallia pustulata and their possible consequences for competitive interactions

“…If the thalli are continuously wet for many days, time differences during final drying could be comparatively unimportant. Continuous rain is not, however, an optimal condition for L. pustulata, as it exhibits a depression of CO 2 uptake rate when the thallus is maximally saturated (Ried 1960;Kappen et al 1996). Indeed, such depression is a general phenomenon in green algal lichens owing to increased diffusion resistance for CO 2 (Lange & Matthes 1981;Lange & Tenhunen 1981).…”