title: Leaf anatomical properties in relation to differences in mesophyll conductance to CO(2)  and photosynthesis in two related Mediterranean Abies species.
abstract: Abies alba and Abies pinsapo are closely related species with the same ribulose 1·5-bisphosphate carboxylase/oxygenase (Rubisco) large subunit (rbcL) but contrasting hydraulic traits and mesophyll structure occurring in the Iberian Peninsula under contrasting conditions. As photosynthesis and hydraulic capacities often co-scale, we hypothesize that these species differ in mesophyll conductance to CO(2)  (g(m) ). g(m)  and key anatomical traits were measured in both species. Drought-adapted population of A. pinsapo has higher photosynthesis than the more mesic population of A. alba, in agreement with its higher hydraulic capacity. However, A. alba exhibits the largest stomatal conductance (g(s) ), and so water use efficiency (WUE) is much higher in A. pinsapo. The differences in photosynthesis were explained by differences in g(m) , indicating a correlation between hydraulic capacity and g(m) . We report a case where g(m)  is the main factor limiting photosynthesis in one species (A. alba) when compared with the other one (A. pinsapo). The results also highlight the discrepancy between g(m)  estimates based on anatomical measurements and those based on gas exchange methods, probably due to the very large resistance exerted by cell walls and the stroma in both species. Thus, the cell wall and chloroplast properties in relation to CO(2)  diffusion constitute a near-future research priority.
authors.affiliation: Grup de Recerca en Biologia de les Plantes en Condicions Mediterrànies, Departament de Biologia, Universitat de les Illes Balears, Carretera de Valldemossa, km 7.5, 07071, Palma de Mallorca, Balears, Spain.
authors.forename: José Javier
authors.initials: JJ
authors.lastname: Peguero-Pina
authors.forename: Jaume
authors.initials: J
authors.lastname: Flexas
authors.forename: Jeroni
authors.initials: J
authors.lastname: Galmés
authors.forename: Ulo
authors.initials: U
authors.lastname: Niinemets
authors.forename: Domingo
authors.initials: D
authors.lastname: Sancho-Knapik
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Barredo
authors.forename: Dido
authors.initials: D
authors.lastname: Villarroya
authors.forename: Eustaquio
authors.initials: E
authors.lastname: Gil-Pelegrín
mesh_terms: D028202:Abies / Q000502:physiology*; D000222:Adaptation, Physiological; D002245:Carbon Dioxide / Q000378:metabolism*; D055864:Droughts; D058503:Mesophyll Cells / Q000502:physiology*; D010788:Photosynthesis; D018515:Plant Leaves; D013045:Species Specificity
chemical_list: D002245:Carbon Dioxide