Abstract
The potential for Crassulacean acid metabolism (CAM) was investigated
in the sandstone outcrop succulent Talinum calycinum in central
Kansas. Field studies revealed CAM-Iike diurnal acid fluctuations in
these plants. These fluctuations persisted under all moisture and temperature
regimes in the laboratory. Despite this CAM-Iike acid metabolism,
simultaneous gravimetric determinations of day- and nighttime transpiration
rates indicated the presence of a d gas exchange pattern. Subsequent
analyses of diurnal CO; and H2O exchange patterns under wellwatered
conditions and after 3, 5, and 7 days of drought confirmed these
findings, though low rates of nocturnal CO, uptake were observed on the
fifth night after continuous drought. Finally, the 6 I 3 C / "C value of this
succulent, - 27.8%c, emphasizes the insignificance of any nocturnal CO..
uptake in the lifelong accumulation of carbon in this species. Thus, it is
proposed that T. calycinum is a ( \ plant with some C AM characteristics,
including the ability to re-fix respiratory COj at night under all moisture
regimes, potentially resulting in a conservation of carbon, and occasionally
to fix atmospheric CO. at night. These findings may prove to be
common among rock outcrop succulents.
Description
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