title: Implications of leaf ontogeny on drought-induced gradients of CAM expression and ABA levels in rosettes of the epiphytic tank bromeliad Guzmania monostachia.
abstract: Guzmania monostachia is an epiphytic heteroblastic bromeliad that exhibits rosette leaves forming water-holding tanks at maturity. Different portions along its leaf blades can display variable degrees of crassulacean acid metabolism (CAM) up-regulation under drought. Since abscisic acid (ABA) can act as an important long-distance signal, we conducted a joint investigation of ontogenetic and drought impacts on CAM intensity and ABA levels in different leaf groups within the G. monostachia rosette. For this, three groups of leaves were analysed according to their position within the mature-tank rosette (i.e., younger, intermediate, and older leaves) to characterize the general growth patterns and magnitude of drought-modulated CAM expression. CAM activity was evaluated by analysing key molecules in the biochemical machinery of this photosynthetic pathway, while endogenous ABA content was comparatively measured in different portions of each leaf group after seven days under well-watered (control) or drought treatment. The results revealed that G. monostachia shows more uniform morphological characteristics along the leaves when in the atmospheric stage. The drought treatment of mature-tank rosettes generally induced in older leaves a more severe water loss, followed by the lowest CAM activity and a higher increase in ABA levels, while younger leaves showed an opposite response. Therefore, leaf groups at distinct ontogenetic stages within the tank rosette of G. monostachia responded to drought with variable degrees of water loss and CAM expression. ABA seems to participate in this tissue-compartmented response as a long-distance signalling molecule, transmitting the drought-induced signals originated in older leaves towards the younger ones.
authors.affiliation: Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, 05508-090, São Paulo, SP, Brazil.
authors.forename: Maria Aurineide
authors.initials: MA
authors.lastname: Rodrigues
authors.affiliation: Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, 05508-090, São Paulo, SP, Brazil.
authors.forename: Leonardo
authors.initials: L
authors.lastname: Hamachi
authors.affiliation: Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, 05508-090, São Paulo, SP, Brazil.
authors.forename: Paulo Tamaso
authors.initials: PT
authors.lastname: Mioto
authors.affiliation: Departamento de Alimentos e Nutrição Experimental, Instituto de Ciências Farmacêuticas, Universidade de São Paulo, 05422-970, São Paulo, SP, Brazil.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Purgatto
authors.affiliation: Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, 05508-090, São Paulo, SP, Brazil. Electronic address: hmercier@usp.br.
authors.forename: Helenice
authors.initials: H
authors.lastname: Mercier
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D031229:Bromeliaceae / Q000378:metabolism* / Q000502:physiology; D055864:Droughts; D010788:Photosynthesis; D018515:Plant Leaves / Q000033:anatomy & histology / Q000378:metabolism*; D015854:Up-Regulation; D014867:Water / Q000378:metabolism
chemical_list: D014867:Water; D000040:Abscisic Acid
keywords: ABA; CAM; Drought; Epiphytes; Guzmania monostachia; Leaf ontogeny; Rosette plants; Tank bromeliad