title: Mesophyll conductance plays a central role in leaf functioning of Oleaceae species exposed to contrasting sunlight irradiance.
abstract: The ability to modify mesophyll conductance (gm ) in response to changes in irradiance may be a component of the acclimation of plants to shade-sun transitions, thus influencing species-specific distributions along light-gradients, and the ecological niches for the different species. To test this hypothesis we grew three woody species of the Oleaceae family, the evergreen Phillyrea latifolia (sun-requiring), the deciduous Fraxinus ornus (facultative sun-requiring) and the hemi-deciduous Ligustrum vulgare (shade tolerant) at 30 or 100% sunlight irradiance. We show that neither mesophyll conductance calculated with combined gas exchange and chlorophyll fluorescence techniques (gm) nor CO2 assimilation significantly varied in F. ornus because of sunlight irradiance. This corroborates previous suggestions that species with high plasticity for light requirements, do not need to undertake extensive reorganization of leaf conductances to CO2 diffusion to adapt to different light environments. On the other hand, gm steeply declined in L. vulgare and increased in P. latifolia exposed to full-sun conditions. In these two species, leaf anatomical traits are in part responsible for light-driven changes in gm , as revealed by the correlation between gm and mesophyll conductance estimated by anatomical parameters (gmA). Nonetheless, gm was greatly overestimated by gmA when leaf metabolism was impaired because of severe light stress. We show that gm is maximum at the light intensity at which plant species have evolved and we conclude that gm actually plays a key role in the sun and shade adaptation of Mediterranean species. The limits of gmA in predicting mesophyll conductance are also highlighted.
authors.affiliation: Dipartimento di Scienze delle Produzioni Agroalimentari e dell'Ambiente, Università di Firenze, Viale delle Idee 30, I-50019, Sesto Fiorentino (FI), Italy.
authors.forename: Alessio
authors.initials: A
authors.lastname: Fini
authors.affiliation: Dipartimento di Scienze Bio-Agroalimentari, Consiglio Nazionale delle Ricerche, P.le Aldo Moro 7, I-00185, Roma, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Loreto
authors.affiliation: Istituto per la Protezione Sostenibile delle Piante, Consiglio Nazionale delle Ricerche, Via Madonna del Piano 10, I-50019, Sesto Fiorentino, Firenze, Italy.
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Tattini
authors.affiliation: Centro di Microscopie Elettroniche "Laura Bonzi", Istituto dei Composti Organometallici, Consiglio Nazionale delle Ricerche, Via Madonna del Piano 10, I-50019, Sesto Fiorentino, Firenze, Italy.
authors.forename: Cristiana
authors.initials: C
authors.lastname: Giordano
authors.affiliation: Dipartimento di Scienze delle Produzioni Agroalimentari e dell'Ambiente, Università di Firenze, Viale delle Idee 30, I-50019, Sesto Fiorentino (FI), Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Ferrini
authors.affiliation: Dipartimento di Scienze delle Produzioni Agroalimentari e dell'Ambiente, Università di Firenze, Viale delle Idee 30, I-50019, Sesto Fiorentino (FI), Italy.|Istituto per la Valorizzazione del Legno e delle Specie Arboree, Consiglio Nazionale delle Ricerche, Via Madonna del Piano 10, I-50019, Sesto Fiorentino, Firenze, Italy.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Brunetti
authors.affiliation: Istituto per la Valorizzazione del Legno e delle Specie Arboree, Consiglio Nazionale delle Ricerche, Via Madonna del Piano 10, I-50019, Sesto Fiorentino, Firenze, Italy.
authors.forename: Mauro
authors.initials: M
authors.lastname: Centritto
mesh_terms: D000064:Acclimatization; D031661:Fraxinus / Q000502:physiology* / Q000528:radiation effects; D058503:Mesophyll Cells / Q000502:physiology / Q000528:radiation effects; D029592:Oleaceae / Q000502:physiology* / Q000528:radiation effects; D018515:Plant Leaves / Q000502:physiology / Q000528:radiation effects; D018526:Plant Transpiration / Q000187:drug effects; D013472:Sunlight