Carbon dioxide exchange in lichens. Carbon dioxide exchange through the cyphellate lower cortex of Sticta latifrons Rich

Carbon dioxide (CO2) exchange of Sticta latifrons Rich. was studied using an infrared gas analyzer. Slight differences in the relationship between net photosynthetic rate (NPR) and water content were found when thalli were dried by using air directed solely onto the upper or lower surfaces. Further studies using a simple split chamber which allowed separate analysis of the CO2exchange of upper and lower thallus surfaces demonstrated that the vast majority of CO2exchanged through the lower surface. The results provide strong circumstantial evidence for the suggestion that cyphellae act as air pores and the possible importance of such pores in the water relations of the species is discussed.