title: Abscisic Acid Induces Rapid Reductions in Mesophyll Conductance to Carbon Dioxide.
abstract: The rate of photosynthesis (A) of plants exposed to water deficit is a function of stomatal (gs) and mesophyll (gm) conductance determining the availability of CO2 at the site of carboxylation within the chloroplast. Mesophyll conductance often represents the greatest impediment to photosynthetic uptake of CO2, and a crucial determinant of the photosynthetic effects of drought. Abscisic acid (ABA) plays a fundamental role in signalling and co-ordination of plant responses to drought; however, the effect of ABA on gm is not well-defined. Rose, cherry, olive and poplar were exposed to exogenous ABA and their leaf gas exchange parameters recorded over a four hour period. Application with ABA induced reductions in values of A, gs and gm in all four species. Reduced gm occurred within one hour of ABA treatment in three of the four analysed species; indicating that the effect of ABA on gm occurs on a shorter timescale than previously considered. These declines in gm values associated with ABA were not the result of physical changes in leaf properties due to altered turgor affecting movement of CO2, or caused by a reduction in the sub-stomatal concentration of CO2 (Ci). Increased [ABA] likely induces biochemical changes in the properties of the interface between the sub-stomatal air-space and mesophyll layer through the actions of cooporins to regulate the transport of CO2. The results of this study provide further evidence that gm is highly responsive to fluctuations in the external environment, and stress signals such as ABA induce co-ordinated modifications of both gs and gm in the regulation of photosynthesis.
authors: Institute for Mediterranean Agriculture and Forest Systems, National Research Council, Via Patacca 85, 80056 Ercolano (NA), Italy.
authors: Giuseppe
authors: G
authors: Sorrentino
authors: Tree and Timber Institute, National Research Council (CNR - IVALSA), Via Madonna del Piano 10, 50019 Sesto Fiorentino (FI), Italy.
authors: Matthew
authors: M
authors: Haworth
authors: Laboratoire de Biotechnologie et Physiologie Végétale, Faculté des Sciences Semlalia, Université Cadi Ayyad, Boulevard My Abdellah BP 2390, Marrakech, Morocco.
authors: Said
authors: S
authors: Wahbi
authors: Department of Environmental Sciences, Pir Mehr Ali Shah Arid Agriculture University, Murree Road, Rawalpindi, Pakistan.
authors: Tariq
authors: T
authors: Mahmood
authors: Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry, Key Lab on Forest Ecology and Environmental Sciences, State Forestry Administration, Beijing, 10091, China.
authors: Shi
authors: S
authors: Zuomin
authors: Tree and Timber Institute, National Research Council (CNR - IVALSA), Via Madonna del Piano 10, 50019 Sesto Fiorentino (FI), Italy.
authors: Mauro
authors: M
authors: Centritto
mesh_terms: D000040:Abscisic Acid / Q000737:chemistry*; D002245:Carbon Dioxide / Q000737:chemistry*; D002462:Cell Membrane / Q000378:metabolism; D002734:Chlorophyll / Q000737:chemistry; D002736:Chloroplasts / Q000502:physiology; D058503:Mesophyll Cells / Q000378:metabolism*; D031658:Olea; D010539:Permeability; D010788:Photosynthesis; D018515:Plant Leaves / Q000502:physiology; D054046:Plant Stomata / Q000502:physiology; D018526:Plant Transpiration / Q000502:physiology*; D032107:Populus; D027861:Prunus; D027826:Rosa; D014867:Water / Q000737:chemistry
chemical_list: D014867:Water; D002734:Chlorophyll; D002245:Carbon Dioxide; D000040:Abscisic Acid