title: Plasticity of crassulacean acid metabolism at subtropical latitudes: a pineapple case study.
abstract: Plants with the crassulacean acid metabolism (CAM) express high-metabolic plasticity, to adjust to environmental stresses. This article hypothesizes that irradiance and nocturnal temperatures are the major limitations for CAM at higher latitudes such as the Azores (37°45'N). Circadian CAM expression in Ananas comosus L. Merr. (pineapple) was assessed by the diurnal pattern of leaf carbon fixation into l-malate at the solstices and equinoxes, and confirmed by determining maximal phosphoenolpyruvate carboxylase (PEPC) activity in plant material. Metabolic adjustments to environmental conditions were confirmed by gas exchange measurements, and integrated with environmental data to determine CAM's limiting factors: light and temperature. CAM plasticity was observed at the equinoxes, under similar photoperiods, but different environmental conditions. In spring, CAM expression was similar between vegetative and flowering plants, while in autumn, flowering (before anthesis) and fructifying (with fully developed fruit before ripening) plants accumulated more l-malate. Below 100 µmol m(-2) s(-1) , CAM phase I was extended, reducing CAM phase III during the day. Carbon fixation inhibition may occur by two major pathways: nocturnal temperature (<15°C) inhibiting PEPC activity and l-malate accumulation; and low irradiance influencing the interplay between CAM phase I and III, affecting carboxylation and decarboxylation. Both have important consequences for plant development in autumn and winter. Observations were confirmed by flowering time prediction using environmental data, emphasizing that CAM expression had a strong seasonal regulation due to a complex network response to light and temperature, allowing pineapple to survive in environments not suitable for high productivity.
authors.affiliation: Instituto de Inovação Tecnológica dos Açores (INOVA), Ponta Delgada, Açores, Portugal.|Centro de Ecologia, Evolução e Alterações Climáticas (CE3C), Faculdade de Ciências, Universidade de Lisboa, Lisboa, Portugal.
authors.forename: Nuno
authors.initials: N
authors.lastname: Rainha
authors.affiliation: Instituto de Inovação Tecnológica dos Açores (INOVA), Ponta Delgada, Açores, Portugal.|Departamento de Ciências Tecnológicas e Desenvolvimento, Universidade dos Açores, Ponta Delgada, Portugal.
authors.forename: Violante P
authors.initials: VP
authors.lastname: Medeiros
authors.affiliation: Instituto de Inovação Tecnológica dos Açores (INOVA), Ponta Delgada, Açores, Portugal.
authors.forename: Mariana
authors.initials: M
authors.lastname: Câmara
authors.affiliation: Instituto de Inovação Tecnológica dos Açores (INOVA), Ponta Delgada, Açores, Portugal.
authors.forename: Hélder
authors.initials: H
authors.lastname: Faustino
authors.affiliation: Instituto de Inovação Tecnológica dos Açores (INOVA), Ponta Delgada, Açores, Portugal.
authors.forename: João P
authors.initials: JP
authors.lastname: Leite
authors.affiliation: Departamento de Ciências Tecnológicas e Desenvolvimento, Universidade dos Açores, Ponta Delgada, Portugal.
authors.forename: Maria do Carmo
authors.initials: Mdo C
authors.lastname: Barreto
authors.affiliation: Centro de Ecologia, Evolução e Alterações Climáticas (CE3C), Faculdade de Ciências, Universidade de Lisboa, Lisboa, Portugal.|Departamento de Biologia Vegetal, Universidade de Lisboa, Faculdade de Ciências, Lisboa, Portugal.
authors.forename: Cristina
authors.initials: C
authors.lastname: Cruz
authors.affiliation: Instituto Superior de Agronomia, Lisboa, Portugal.
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Pacheco
authors.affiliation: Instituto de Inovação Tecnológica dos Açores (INOVA), Ponta Delgada, Açores, Portugal.|Departamento de Ciências Tecnológicas e Desenvolvimento, Universidade dos Açores, Ponta Delgada, Portugal.
authors.forename: Duarte
authors.initials: D
authors.lastname: Ponte
authors.affiliation: Departamento de Biologia Vegetal, Universidade de Lisboa, Faculdade de Ciências, Lisboa, Portugal.|Biosystems & Integrative Sciences Institute (BioISI), Universidade de Lisboa, Faculdade de Ciências, Lisboa, Portugal.
authors.forename: Anabela
authors.initials: A
authors.lastname: Bernardes da Silva
mesh_terms: D031230:Ananas / Q000502:physiology* / Q000528:radiation effects; D057486:Carbon Cycle; D002980:Climate; D004777:Environment; D035264:Flowers / Q000502:physiology / Q000528:radiation effects; D018506:Gene Expression Regulation, Plant; D008027:Light; D008293:Malates / Q000378:metabolism*; D017440:Photoperiod; D018515:Plant Leaves / Q000502:physiology / Q000528:radiation effects; D018526:Plant Transpiration / Q000502:physiology; D012621:Seasons; D013696:Temperature; D013997:Time Factors
chemical_list: D008293:Malates; C030298:malic acid