title: The photosynthetic plasticity of crassulacean acid metabolism: an evolutionary innovation for sustainable productivity in a changing world.
abstract: The photosynthetic specialization of crassulacean acid metabolism (CAM) has evolved many times in response to selective pressures imposed by water limitation. Integration of circadian and metabolite control over nocturnal C₄ and daytime C₃ carboxylation processes in CAM plants provides plasticity for optimizing carbon gain and water use by extending or curtailing the period of net CO₂ uptake over any 24-h period. Photosynthetic plasticity underpins the ecological diversity of CAM species and contributes to the potential for high biomass production in water-limited habitats. Perceived evolutionary constraints on the dynamic range of CO₂ acquisition strategies in CAM species can be reconciled with functional anatomical requirements and the metabolic costs of maintaining the enzymatic machinery required for C₃ and C₄ carboxylation processes. Succulence is highlighted as a key trait for maximizing biomass productivity in water-limited habitats by serving to buffer water availability, by maximizing the magnitude of nocturnal CO₂ uptake and by extending the duration of C₄ carboxylation beyond the night period. Examples are discussed where an understanding of the diverse metabolic and ecological manifestations of CAM can be exploited for the sustainable productivity of economically and ecologically important species.
authors.affiliation: School of Biology, Newcastle University, Newcastle Upon Tyne NE1 7RU, UK.
authors.forename: Anne M
authors.initials: AM
authors.lastname: Borland
authors.affiliation: School of Biology, Newcastle University, Newcastle Upon Tyne NE1 7RU, UK.
authors.forename: V Andrea
authors.initials: VA
authors.lastname: Barrera Zambrano
authors.affiliation: School of Biology, Newcastle University, Newcastle Upon Tyne NE1 7RU, UK.|Department of Biosystems, Division of Crop Biotechnics, Katholieke Universiteit Leuven, Willem De Croylaan 42, B-3001 Heverlee, Belgium.
authors.forename: Johan
authors.initials: J
authors.lastname: Ceusters
authors.affiliation: School of Biology, Newcastle University, Newcastle Upon Tyne NE1 7RU, UK.
authors.forename: Katherine
authors.initials: K
authors.lastname: Shorrock
mesh_terms: D005075:Biological Evolution; D002245:Carbon Dioxide / Q000378:metabolism*; D057906:Circadian Clocks; D018556:Crops, Agricultural / Q000191:economics / Q000254:growth & development; D055864:Droughts; D017753:Ecosystem; D008027:Light; D010730:Phosphoenolpyruvate Carboxylase / Q000378:metabolism; D010788:Photosynthesis / Q000235:genetics*; D018521:Plant Physiological Phenomena; D010944:Plants / Q000033:anatomy & histology / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism; D012621:Seasons; D013045:Species Specificity; D014867:Water / Q000378:metabolism*
chemical_list: D014867:Water; D002245:Carbon Dioxide; D010730:Phosphoenolpyruvate Carboxylase; D012273:Ribulose-Bisphosphate Carboxylase