Carbon Dioxide Exchange in Lichens

Publisher Website
Google Scholar
Abstract
The relationship between net photosynthesis and CO2 concentration was investigated for 4 spp. of lichen [Peltigera dolichorhiza, Pseudocyphellaria billardierii, Sticta latifrons and S. ramulosum] using an IR gas analyzer operating in a closed loop system. All species showed a linear relationship at low CO2 levels (100 .mu.l/l), with CO2 saturation levels being in excess of 400 .mu.l/l. Detailed studies of S. latifrons showed a strong influence of thallus water content, which resulted in the net photosynthetic response at high water contents still being nearly linear at 1000 .mu.l/l CO2. Very low CO2 compensation values (5 .mu.l/l) were obtained under some conditions, but the value varied between thalli and with thallus water content. The results differ from previous studies which reported low CO2 saturation levels (200 .mu.l/l) and no apparent effect of water content. Some of these differences may result from the use of a discrete sampling injection IR gas analyzer system in the earlier studies, and an assessment is made of the influence of nonsaturating CO2 levels, lack of cuvette ventilation and data presentation for this technique.