Crassulacean acid metabolism in australian vascular epiphytes and some related species
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The occurrence of crassulacean acid metabolism (CAM) among epiphytes and related plant species from tropical and subtropical rainforests in Eastern Australia was investigated. As judged from δ13C value and the absence of Kranz anatomy, indications of CAM were found in 66 species belonging to the families, Polypodiaceae (3), Orchidaceae (55), Asclepiadaceae (6) and Rubiaceae (2).
Two thirds of orchidaceous plants examined appeared to use CAM. Those species with thicker leaves generally had less negative δ13C values, as did those species growing on more exposed sites; leaves thicker than about 1 mm in most species yielded δ13C values indicative of pronounced CAM. Two leafless species, Chiloschista phyllorhiza and Taeniophyllum malianum, which depend on chloroplast-containing, stomata-less roots for photosynthesis also showed δ13C values typical of CAM. Pseudobulbs and swollen stems, a characteristic of many orchids, were usually somewhat enriched in 13C compared to corresponding leaves.
In Polypodiaceae CAM was found in the genus Pyrrosia. While δ13C values were generally less negative with increasing frond thickness, the leaf morphology was extremely variable within species. Pyrrosia confluens plants from shaded habitats had long, relatively thin and darkgreen fronds whereas specimens from sun-exposed sites were characterized by short, thick, bleached fronds. Both types showed the capacity for nocturnal accumulation of titratable acidity and exhibited continuous net CO2 fixation during 12 h light/12 h dark cycles under laboratory conditions. Shade-fronds showed this capacity even when irradiance was lower than 2% of full sunlight during the 12 h light period.
In Asclepiadaceae CAM was found in species of two genera which usually have fleshy leaves, Hoya and Dischidia. In Rubiaceae CAM was recorded in two genera of epiphytic ant plants, Hydnophytum and Myrmecodia.
It is concluded that CAM is widespread in Australian epiphytes. It is most prevalent in species found in exposed microhabitats where the growing conditions are characterised by relatively high light intensities and short but frequent periods of water stress.
KeywordsTitratable Acidity Crassulacean Acid Metabolism Full Sunlight Exposed Site Related Plant Species
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- Benzing DH (1980) The biology of the Bromeliads. Mad River Press Inc., CaliforniaGoogle Scholar
- Benzing DH, Ott DW (1981) Vegetative reduction in epiphytic Bromeliaceae and Orchidaceae: Its origin and significance. Biotropica 13:131–140Google Scholar
- Coutinho LM (1969) Novas observacoes a ocorrenica do “efeito de de Sassure” e suas relacoes com a suculencia, a temperatura folhear e os movimentos estomaticos. Botanica 24:79–102Google Scholar
- Farquhar GD, Ball MC, von Caemmerer S, Roksandic Z (1982) Effect of salinity and humidity on δ13C value of halophytes — evidence for diffusional isotope fractionation determined by the ratio of intercellular/atmospheric partial pressure of CO2 under different environnmental conditions. Oecologia (Berlin) 52:121–124Google Scholar
- Gessner F (1956) Der Wasserhaushalt der Epiphyten und Lianen. In Ruhland W (ed) Handbuch der Pflanzenphysiologie Bd III, Pflanze und Wasser. Springer, Berlin Göttingen Heidelberg, 938–950Google Scholar
- Goh CJ, Avadhani PN, Loh CS, Hanegraaf C, Arditti J (1977) Diurnal stomatal and acidity rhythms in orchid leaves. New Phytol 78:365–372Google Scholar
- Hohorst HJ (1970) L-(-)-Malat, Bestimmung mit Malatdehydrogenase und NAD. In Bergmeyer HU (ed) Methoden der enzymatischen Analyse Bd II. Verlag Chemie, Weinheim, 1544–1548Google Scholar
- Kausch W (1965) Beziehungen zwischen Wurzelwachstum. Transpiration und CO2-Gaswechsel bei einigen Kakteen. Planta 66:229–238Google Scholar
- Medina E (1975) Dark CO2 fixation, habitat preference and evolution within the Bromeliaceae. Evolution 28:677–686Google Scholar
- Medina E, Delgado M (1976) Photosynthesis and night CO2 fixation in Echeveria columbiana v. Poellnitz. Photosynthetica 10:155–163Google Scholar
- Medina E, Delgado M, Troughton JH, Medina JD (1977) Physiological ecology of CO2 fixation in Bromeliaceae. Flora 166:137–152Google Scholar
- Medina E, Minchin P (1980) Stratification of δ13C values of leaves in Amazonian rain forests. Oecologia (Berlin) 45:377–378Google Scholar
- Medina E, Troughton JH (1974) Dark CO2 fixation and carbon isotope ratio in Bromeliaceae. Plant Sci Lett 2:357–362Google Scholar
- Neales TF, Hew CS (1975) Two types of carbon fixation in tropical orchids. Planta 123:303–306Google Scholar
- O'leary MH (1981) Carbon isotope fractionation in plants. Phytochem 20:553–567Google Scholar
- Osmond CB, Nott DL, Firth PM (1979) Carbon assimilation patterns and growth of the introduced CAM plant Opuntia inermis in Eastern Australia. Oecologia (Berlin) 40:331–350Google Scholar
- Powles SB, Osmond CB (1978) Inhibition of the capacity and efficiency of photosynthesis in bean leaflets illuminated in a CO2-free atmosphere at Low O2: a possible role for photorespiration. Aust J Plant Physiol 5:619–629Google Scholar
- Powles SB, Osmond CB, Thorne SW (1979) Photoinhibition of intact attached leaves of C3 plants illuminated in the absence of both carbon dioxide and photorespiration. Plant Physiol 64:982–988Google Scholar
- Richards PW (1952) The tropical rainforest. Camb Univ Press, London-New York-MelbourneGoogle Scholar
- Rowley G (1978) Illustrated encyclopedia of succulents. Salamander, LondonGoogle Scholar
- Szarek SR, Ting IP (1974) Seasonal patterns of acid metabolism and gas exchange in Opuntia basilaris. Plant Physiol 54:76–81Google Scholar
- Teeri JA, Tonsor SJ, Turner M (1981) Leaf thickness and carbon isotope composition in the Crassulaceae. Oecologia (Berlin) 50: 367–369Google Scholar
- Wallace BJ (1982) The Australian vascular epiphytes: flora and ecology. PhD thesis, Univ New England, Armidale, AustraliaGoogle Scholar
- Walter H (1951) Grundlagen der Pflanzenverbreitung 1. Teil: Standortslehre. Ulmer, StuttgartGoogle Scholar
- Willis JC, Airy Shaw HK (1973) A dictionary of the flowering plants and ferns. Camb Univ Press, London-New YorkGoogle Scholar
- Winter K, Osmon CB, Pate JS (1981) Coping with salinity. In Pate JS, McComb AJ (eds) The biology of Australian plants. University of Western Australia Press, Nedlands, 88–113Google Scholar
- Wong SC, Hew CS (1976) Diffusive resistance, titratable acidity, and CO2 fixation in two tropical epiphytic ferns. Amer Fern J 66:121–124Google Scholar