Variability in Crassulacean Acid Metabolism: A Survey of North Carolina Succulent Species

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Abstract
The correlation between succulence and crassulacean acid metabolism (CAM) was investigated in 28 succulent species growing in various habitats throughout North Carolina. Three species (Opuntia compressa, Agave virginica and Tillandsia usneoides) exhibited diurnal fluctuations in tissue titratable acidity, nighttime uptake of 14CO2, and a high C isotope ratio (.delta.13C), all indicators of CAM. Seven species displayed 1 or 2 characteristics of CAM in situ yet yielded lower .delta.13C values, indicating a partial or total restriction of atmospheric CO2 uptake to the C3 photosynthetic system: Yucca gloriosa, Sesuvium maritimum, Talinum teretifolium, Diamorpha smallii, Sedum pusillum, S. nevii and S. telephioides. Several of these species were apparently capable of utilizing the CAM pathway to fix internal respiratory CO2. The results emphasize that 1 photosynthetic pathway does not characterize all succulents in North Carolina.