title: Coordination of stomatal physiological behavior and morphology with carbon dioxide determines stomatal control.
abstract: OBJECTIVE
  Stomatal control is determined by the ability to alter stomatal aperture and/or the number of stomata on the surface of new leaves in response to growth conditions. The development of stomatal control mechanisms to the concentration of CO₂within the atmosphere ([CO₂]) is fundamental to our understanding of plant evolutionary history and the prediction of gas exchange responses to future [CO₂].
  
  
  METHODS
  In a controlled environment, fern and angiosperm species were grown in atmospheres of ambient (400 ppm) and elevated (2000 ppm) [CO₂]. Physiological stomatal behavior was compared with the stomatal morphological response to [CO₂].
  
  
  RESULTS
  An increase in [CO₂] or darkness induced physiological stomatal responses ranging from reductions (active) to no change (passive) in stomatal conductance. Those species with passive stomatal behavior exhibited pronounced reductions of stomatal density in new foliage when grown in elevated [CO₂], whereas species with active stomata showed little morphological response to [CO₂]. Analysis of the physiological and morphological stomatal responses of a wider range of species suggests that patterns of stomatal control to [CO₂] do not follow a phylogenetic pattern associated with plant evolution.
  
  
  CONCLUSIONS
  Selective pressures may have driven the development of divergent stomatal control strategies to increased [CO₂]. Those species that are able to actively regulate guard cell turgor are more likely to respond to [CO₂] through a change in stomatal aperture than stomatal number. We propose a model of stomatal control strategies in response to [CO₂] characterized by a trade-off between short-term physiological behavior and longer-term morphological response.
authors.affiliation: CNR-Istituto di Biometeorologia (IBIMET), Via Giovanni Caproni 8 50145 Florence, Italy.
authors.forename: Matthew
authors.initials: M
authors.lastname: Haworth
authors.affiliation: Department of Agrifood Production and Environmental Sciences (DiSPAA), University of Florence, Piazzale delle Cascine 28 50144 Florence, Italy Institute of Natural and Applied Science, Çanakkale Onsekiz Mart University 17020 Çanakkale, Turkey.
authors.forename: Dilek
authors.initials: D
authors.lastname: Killi
authors.affiliation: CNR-Istituto di Biometeorologia (IBIMET), Via Giovanni Caproni 8 50145 Florence, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Materassi
authors.affiliation: CNR-Istituto di Biometeorologia (IBIMET), Via Giovanni Caproni 8 50145 Florence, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Raschi
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism*; D029624:Ferns / Q000033:anatomy & histology* / Q000502:physiology*; D019684:Magnoliopsida / Q000033:anatomy & histology* / Q000502:physiology*; D010802:Phylogeny; D054046:Plant Stomata / Q000033:anatomy & histology / Q000502:physiology; D013045:Species Specificity
chemical_list: D002245:Carbon Dioxide
keywords: carbon dioxide; stomatal behavior; stomatal density; stomatal evolution; stomatal index