title: Light acclimation of photosynthesis in two closely related firs (Abies pinsapo Boiss. and Abies alba Mill.): the role of leaf anatomy and mesophyll conductance to CO2.
abstract: Leaves growing in the forest understory usually present a decreased mesophyll conductance (gm) and photosynthetic capacity. The role of leaf anatomy in determining the variability in gm among species is known, but there is a lack of information on how the acclimation of gm to shade conditions is driven by changes in leaf anatomy. Within this context, we demonstrated that Abies pinsapo Boiss. experienced profound modifications in needle anatomy to drastic changes in light availability that ultimately led to differential photosynthetic performance between trees grown in the open field and in the forest understory. In contrast to A. pinsapo, its congeneric Abies alba Mill. did not show differences either in needle anatomy or in photosynthetic parameters between trees grown in the open field and in the forest understory. The increased gm values found in trees of A. pinsapo grown in the open field can be explained by occurrence of stomata at both needle sides (amphistomatous needles), increased chloroplast surface area exposed to intercellular airspace, decreased cell wall thickness and, especially, decreased chloroplast thickness. To the best of our knowledge, the role of such drastic changes in ultrastructural needle anatomy in explaining the response of gm to the light environment has not been demonstrated in field conditions.
authors.affiliation: Unidad de Recursos Forestales, Centro de Investigación y Tecnología Agroalimentaria, Gobierno de Aragón, Avenida Montañana 930, 50059 Zaragoza, Spain.
authors.forename: José Javier
authors.initials: JJ
authors.lastname: Peguero-Pina
authors.affiliation: Unidad de Recursos Forestales, Centro de Investigación y Tecnología Agroalimentaria, Gobierno de Aragón, Avenida Montañana 930, 50059 Zaragoza, Spain.
authors.forename: Domingo
authors.initials: D
authors.lastname: Sancho-Knapik
authors.affiliation: Research Group on Plant Biology under Mediterranean Conditions, Departament de Biologia, Universitat de les Illes Balears, Carretera de Valldemossa, 07071 Palma de Mallorca, Spain.
authors.forename: Jaume
authors.initials: J
authors.lastname: Flexas
authors.affiliation: Research Group on Plant Biology under Mediterranean Conditions, Departament de Biologia, Universitat de les Illes Balears, Carretera de Valldemossa, 07071 Palma de Mallorca, Spain.
authors.forename: Jeroni
authors.initials: J
authors.lastname: Galmés
authors.affiliation: Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, Kreutzwaldi 1, Tartu 51014, Estonia.
authors.forename: Ülo
authors.initials: Ü
authors.lastname: Niinemets
authors.affiliation: Unidad de Recursos Forestales, Centro de Investigación y Tecnología Agroalimentaria, Gobierno de Aragón, Avenida Montañana 930, 50059 Zaragoza, Spain egilp@aragon.es.
authors.forename: Eustaquio
authors.initials: E
authors.lastname: Gil-Pelegrín
mesh_terms: D028202:Abies / Q000502:physiology* / Q000528:radiation effects; D000064:Acclimatization / Q000528:radiation effects*; D002245:Carbon Dioxide / Q000378:metabolism*; D008027:Light; D058503:Mesophyll Cells / Q000166:cytology / Q000378:metabolism* / Q000528:radiation effects; D010788:Photosynthesis / Q000528:radiation effects*; D018515:Plant Leaves / Q000033:anatomy & histology* / Q000528:radiation effects; D013030:Spain
chemical_list: D002245:Carbon Dioxide
keywords: cell wall; chloroplast thickness; forest understory