CO2 -Gaswechsel der Flechte Hypogymnia physodes bei tiefen Temperaturen im Freiland

Abstract

Summary Measurements of the CO2-gas-exchange of the lichen Hypogymnia physodes at low temperatures in the field During late winter 1968 (March) the CO2-gas-exchange of the lichen Hypogymnia physodes was measured in its natural habitat under natural conditions as well as under controlled temperature conditions. Though temperature did not increase above 4°C, temporary it was only 0 °C, and light intensity was just low because of snow showers, the net photosynthesis of the lichen was positive all day long. Daily CO2-uptake was 22 mg • dm−2 (referred to thallus surface). Maximum rate of CO2-net-photosynthesis was 3.8 mg CO2 • dm−2 • h−1 • Even at - 6°C, 0.44 mg CO2 • dm−2• h−1 were assimilated. The results confirm the results found in the laboratory about the photosynthetic activity of lichens at low temperatures. Comparing the rate of photosynthesis of Hypogymnia at temperatures near and below freezing with the photosynthetic activity of higher plants it shows up that these rates might be ecologically rather important for the annual CO2-balance.