Facultative crassulacean acid metabolism (CAM) in four small C-3 and C-4 leaf-succulents

Winter, Klaus, and Holtum, Joseph A.M. (2017) Facultative crassulacean acid metabolism (CAM) in four small C-3 and C-4 leaf-succulents. Australian Journal of Botany, 65 (2). pp. 103-108.

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Measurements of whole-plant gas exchange and titratable acidity demonstrate that the Australian native species Anacampseros australiana J.M.Black (Anacampserotaceae), Crassula sieberiana (Schult. & Schult.f.) Druce (Crassulaceae) and Portulaca australis Endl. (Portulacaceae) and the widespread naturalised tropical exotic, Portulaca pilosa L., exhibit facultative crassulacean acid metabolism (CAM). In well-watered plants, net CO2 uptake was restricted to the daylight hours and occurred via the C-3 pathway (A. australiana and C. sieberiana) or the C-4 pathway (P. australis and P. pilosa). Leaves of well-watered plants did not accumulate titratable acidity during the night. Following drought treatment, CO2 uptake in the light by shoots decreased markedly, nocturnal gas-exchange shifted from net CO2 loss to a CAM-type pattern that included net CO2 uptake, and leaves acidified at night. Nocturnal CO2 uptake by shoots and leaf acidification were most pronounced in A. australiana and least so in C. sieberiana. The induction of dark CO2 uptake and tissue acidification was fully reversible in all four species: upon rewatering, nocturnal CO2 uptake and acidification ceased and the rates of CO2 incorporation in the light were restored. Wesuggest that, hitherto considered relatively exceptional globally, facultative CAM may be more common than previously suspected, particularly among the generally small ephemeral leaf-succulents that characterise Australia's succulent flora.

Item ID: 50279
Item Type: Article (Research - C1)
ISSN: 1444-9862
Keywords: Anacampseros, C-4 photosynthesis, Crassula, functional diversity, photosynthetic pathway, Portulaca
Funders: Australian Research Council (ARC), Smithsonian Tropical Research Institute
Projects and Grants: ARC DP160100098
Date Deposited: 20 Sep 2017 07:30
FoR Codes: 31 BIOLOGICAL SCIENCES > 3108 Plant biology > 310806 Plant physiology @ 100%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970106 Expanding Knowledge in the Biological Sciences @ 100%
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