Is Sedum acre L. a CAM plant?

Sedum acre L. collected from its natural stands south of Darmstadt (Germany) showed δ13C values typical for C3 plants. This suggests that in situ at the natural stand CO2 was fixed mainly via the C3 mode of photosynthesis rather than via the CAM mode. However, experimental water stress shifts the CO2 exchange pattern from the C3 type to CAM type. Simultaneously, a diurnal rhythm of malic acid oscillation, typical for CAM, and increase of PEP-carboxylase and malic enzyme activities developed. Hence, Sedum acre is obviously to be classified as a facultative CAM plant. Because of the temperature characteristics of CO2 exchange in Sedum acre, in situ CO2 should be harvested from the atmosphere mainly during the seasons where water stress situations capable of inducing CAM are unlikely to occur.