title: Carbon isotope discrimination in alpine succulent plants supposed to be capable of crassulacean acid metabolism (CAM).
abstract: 1. The 4 alpine species of Sempervivum (S. arachnoideum L., S. montanum L., S. soboliferum Sims, S. wulfenii Hoppe) analyzed in this study showed acidification during the dark period in their natural habitat. The δ13C value of these species varied according to the water supply at their natural habitat, being less negative at dry sites. These data are consistent with a larger contribution of dark CO2fixation via Phosphoenolpyruvate-Carboxylase in relation to light CO2fixation via Ribulose-1, 5-diphosphate Carboxylase. These alpine Sempervivum spp. behave, therefore, like typical CAM-plants. 2. In contrast, the 3 alpine species of Sedum analyzed in this respect (S. acre. L., S. alpestre Vill., S. rosea (L.) Scop.) showed no pronounced dark acidification. The δ13C value of the 8 alpine Sedum species examined in this study (the 3 mentioned above and S. album L., S. atratum L., S. dasyphyllum L., S. reflexum L., S. sexangulare L.) was much more negative than in the Sempervivum spp., indicating that the dark CO2fixation does not play a great role in the carbon metabolism of the alpine Sedum spp. in the natural habitats. Water supply in the natural habitat has no clear-cut influence on the δ13C value. 3. All alpine species of Saxifraga analysed (S. seloides L., S. oppositifolia L., S. bryoides L., S. aizoides L., S. squarrosa Sieber, S. paniculata Mill., S. caesia L.) show δ13C values typical of C3plants and they were not influended by the water conditions in the natural sites. Saxifraga paniculata showed no dark acidification in its natural habitat and we suspect that alpine Saxifrages are not CAM plants. 4. Based on δ13C values the alpine plants Pinguicula alpina L., Thesium alpinum L., and Linaria alpina (L.) Mill. are typical C3plants.
authors.affiliation: Botanisches Institut der Technischen Universität München, München, Germany.|Institut für radiohydrometrie der Gesellschaft für Strahlen- und Umweltforschung mbH, München.|Department of Environmental Biology, Australian National University, Canberra, Australia.
authors.forename: C B
authors.initials: CB
authors.lastname: Osmond
authors.affiliation: Botanisches Institut der Technischen Universität München, München, Germany.|Institut für Botanik und Mikrobiologie der Technischen Universität, Arcisstr. 21, D-8000, München 2, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Ziegler
authors.affiliation: Institut für radiohydrometrie der Gesellschaft für Strahlen- und Umweltforschung mbH, München.
authors.forename: W
authors.initials: W
authors.lastname: Stichler
authors.affiliation: Institut für radiohydrometrie der Gesellschaft für Strahlen- und Umweltforschung mbH, München.
authors.forename: P
authors.initials: P
authors.lastname: Trimborn