Is Sedum acre L. a CAM plant?

Sedum acre L. collected from its natural stands south of Darmstadt (Germany) showed δC values typical for C plants. This suggests that in situ at the natural stand CO was fixed mainly via the C mode of photosynthesis rather than via the CAM mode. However, experimental water stress shifts the CO exchange pattern from the C 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 CO exchange in Sedum acre, in situ CO should be harvested from the atmosphere mainly during the seasons where water stress situations capable of inducing CAM are unlikely to occur.