Australia Lacks Stem Succulents but Is It Depauperate in Plants With
Available online at www.sciencedirect.com ScienceDirect Australia lacks stem succulents but is it depauperate in plants with crassulacean acid metabolism (CAM)? 1,2 3 3 Joseph AM Holtum , Lillian P Hancock , Erika J Edwards , 4 5 6 Michael D Crisp , Darren M Crayn , Rowan Sage and 2 Klaus Winter In the flora of Australia, the driest vegetated continent, [1,2,3]. Crassulacean acid metabolism (CAM), a water- crassulacean acid metabolism (CAM), the most water-use use efficient form of photosynthesis typically associated efficient form of photosynthesis, is documented in only 0.6% of with leaf and stem succulence, also appears poorly repre- native species. Most are epiphytes and only seven terrestrial. sented in Australia. If 6% of vascular plants worldwide However, much of Australia is unsurveyed, and carbon isotope exhibit CAM [4], Australia should host 1300 CAM signature, commonly used to assess photosynthetic pathway species [5]. At present CAM has been documented in diversity, does not distinguish between plants with low-levels of only 120 named species (Table 1). Most are epiphytes, a CAM and C3 plants. We provide the first census of CAM for the mere seven are terrestrial. Australian flora and suggest that the real frequency of CAM in the flora is double that currently known, with the number of Ellenberg [2] suggested that rainfall in arid Australia is too terrestrial CAM species probably 10-fold greater. Still unpredictable to support the massive water-storing suc- unresolved is the question why the large stem-succulent life — culent life-form found amongst cacti, agaves and form is absent from the native Australian flora even though euphorbs.
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