Lichen photosynthesis in relation to CO concentration.

Photosynthetic CO 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 CO concentrations at the lower range of CO values, but little photosynthetic variation with increasing CO concentrations at the upper range of CO values. Half maximal CO concentration estimates varied from 147-440 μl CO·l, but had broadly overlapping confidence intervals. We conclude that lichen CO dependencies are basically similar to those reported for higher plants and discuss the reasons why widely varying results have previously been published.