Lichen photosynthesis in relation to CO2 concentration.

Photosynthetic CO2 dependencies were measured for six lichen species, representing a variety of morphologies and collected from widely different habitats. All curves exhibited a linear increase in photosynthesis with increasing CO2 concentrations at the lower range of CO2 values, but little photosynthetic variation with increasing CO2 concentrations at the upper range of CO2 values. Half maximal CO2 concentration estimates varied from 147-440 μl CO2·l1, but had broadly overlapping confidence intervals. We conclude that lichen CO2 dependencies are basically similar to those reported for higher plants and discuss the reasons why widely varying results have previously been published.