title: Two Hymenophyllaceae species from contrasting natural environments exhibit a homoiochlorophyllous strategy in response to desiccation stress.
abstract: Hymenophyllaceae is a desiccation tolerant family of Pteridophytes which are poikilohydric epiphytes. Their fronds are composed by a single layer of cells and lack true mesophyll cells and stomata. Although they are associated with humid and shady environments, their vertical distribution varies along the trunk of the host plant with some species inhabiting the drier sides with a higher irradiance. The aim of this work was to compare the structure and function of the photosynthetic apparatus during desiccation and rehydration in two species, Hymenophyllum dentatum and Hymenoglossum cruentum, isolated from a contrasting vertical distribution along the trunk of their hosts. Both species were subjected to desiccation and rehydration kinetics to analyze frond phenotypic plasticity, as well as the structure, composition and function of the photosynthetic apparatus. Minimal differences in photosynthetic pigments were observed upon dehydration. Measurements of ϕPSII (effective quantum yield of PSII), ϕNPQ (quantum yield of the regulated energy dissipation of PSII), ϕNO (quantum yield of non-regulated energy dissipation of PSII), and TL (thermoluminescence) indicate that both species convert a functional photochemical apparatus into a structure which exhibits maximum quenching capacity in the dehydrated state with minimal changes in photosynthetic pigments and polypeptide compositions. This dehydration-induced conversion in the photosynthetic apparatus is completely reversible upon rehydration. We conclude that H. dentatum and H. cruentum are homoiochlorophyllous with respect to desiccation stress and exhibited no correlation between inherent desiccation tolerance and the vertical distribution along the host tree trunk.
authors.affiliation: Departamento de Botánica, Facultad de Ciencias Naturales y Oceanográficas, Universidad de Concepción, Chile. Electronic address: alejandrafloresbavestrello@gmail.com.
authors.forename: Alejandra
authors.initials: A
authors.lastname: Flores-Bavestrello
authors.affiliation: Department of Biology and The Biotron Centre for Experimental Climate Change Research, Western University, London, Ontario, N6A 5B7, Canada. Electronic address: mkrol@uwo.ca.
authors.forename: Marianna
authors.initials: M
authors.lastname: Król
authors.affiliation: Department of Biology and The Biotron Centre for Experimental Climate Change Research, Western University, London, Ontario, N6A 5B7, Canada. Electronic address: aivanov@uwo.ca.
authors.forename: Alexander G
authors.initials: AG
authors.lastname: Ivanov
authors.affiliation: Department of Biology and The Biotron Centre for Experimental Climate Change Research, Western University, London, Ontario, N6A 5B7, Canada. Electronic address: nhuner@uwo.ca.
authors.forename: Norman P A
authors.initials: NP
authors.lastname: Hüner
authors.affiliation: Departamento de Biología Vegetal y Ecología, Universidad del País Vasco (UPV/EHU), Aptdo. 644, E-48080 Bilbao, Spain. Electronic address: joseignacio.garcia@ehu.es.
authors.forename: José Ignacio
authors.initials: JI
authors.lastname: García-Plazaola
authors.affiliation: Departamento de Botánica, Facultad de Ciencias Naturales y Oceanográficas, Universidad de Concepción, Chile. Electronic address: lcorcuer@udec.cl.
authors.forename: Luis J
authors.initials: LJ
authors.lastname: Corcuera
authors.affiliation: Departamento de Ciencias Agronómicas y Recursos Naturales, Facultad de Ciencias Agronómicas y Forestales, Universidad de La Frontera, Chile; Center of Plant, Soil Interaction and Natural Resources Biotechnology, Scientific and Technological Bioresource Nucleus, Universidad de La Frontera, Chile. Electronic address: leon.bravo@ufrontera.cl.
authors.forename: León A
authors.initials: LA
authors.lastname: Bravo
mesh_terms: D002734:Chlorophyll / Q000378:metabolism*; D003890:Desiccation; D004579:Electron Transport / Q000528:radiation effects; D004591:Electrophoresis, Polyacrylamide Gel; D004777:Environment; D029624:Ferns / Q000378:metabolism* / Q000528:radiation effects; D008027:Light; D049449:Luminescence; D010788:Photosynthesis / Q000528:radiation effects; D045331:Photosystem I Protein Complex / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000378:metabolism; D018515:Plant Leaves / Q000033:anatomy & histology / Q000528:radiation effects; D013312:Stress, Physiological / Q000528:radiation effects; D013696:Temperature
chemical_list: D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D002734:Chlorophyll
keywords: Desiccation tolerance; Filmy ferns; Homoiochlorophyllous; Hymenophyllaceae; Poikilohydric