title: Arbuscular mycorrhizal symbiosis increases relative apoplastic water flow in roots of the host plant under both well-watered and drought stress conditions.
abstract: OBJECTIVE
  The movement of water through mycorrhizal fungal tissues and between the fungus and roots is little understood. It has been demonstrated that arbuscular mycorrhizal (AM) symbiosis regulates root hydraulic properties, including root hydraulic conductivity. However, it is not clear whether this effect is due to a regulation of root aquaporins (cell-to-cell pathway) or to enhanced apoplastic water flow. Here we measured the relative contributions of the apoplastic versus the cell-to-cell pathway for water movement in roots of AM and non-AM plants.
  
  
  METHODS
  We used a combination of two experiments using the apoplastic tracer dye light green SF yellowish and sodium azide as an inhibitor of aquaporin activity. Plant water and physiological status, root hydraulic conductivity and apoplastic water flow were measured.
  
  
  RESULTS
  Roots of AM plants enhanced significantly relative apoplastic water flow as compared with non-AM plants and this increase was evident under both well-watered and drought stress conditions. The presence of the AM fungus in the roots of the host plants was able to modulate the switching between apoplastic and cell-to-cell water transport pathways.
  
  
  CONCLUSIONS
  The ability of AM plants to switch between water transport pathways could allow a higher flexibility in the response of these plants to water shortage according to the demand from the shoot.
authors.affiliation: Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín (EEZ-CSIC), Profesor Albareda no. 1, Granada, Spain.
authors.forename: Gloria
authors.initials: G
authors.lastname: Bárzana
authors.forename: Ricardo
authors.initials: R
authors.lastname: Aroca
authors.forename: José Antonio
authors.initials: JA
authors.lastname: Paz
authors.forename: François
authors.initials: F
authors.lastname: Chaumont
authors.forename: Mari Carmen
authors.initials: MC
authors.lastname: Martinez-Ballesta
authors.forename: Micaela
authors.initials: M
authors.lastname: Carvajal
authors.forename: Juan Manuel
authors.initials: JM
authors.lastname: Ruiz-Lozano
mesh_terms: D020346:Aquaporins / Q000037:antagonists & inhibitors / Q000378:metabolism; D055864:Droughts; D018506:Gene Expression Regulation, Plant; D008086:Lissamine Green Dyes; D018551:Solanum lycopersicum / Q000254:growth & development / Q000382:microbiology / Q000502:physiology*; D038821:Mycorrhizae / Q000254:growth & development / Q000502:physiology*; D010788:Photosynthesis / Q000502:physiology; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D018517:Plant Roots / Q000254:growth & development / Q000382:microbiology / Q000502:physiology; D054046:Plant Stomata / Q000502:physiology; D018526:Plant Transpiration / Q000502:physiology; D019810:Sodium Azide / Q000494:pharmacology; D012987:Soil; D013559:Symbiosis / Q000502:physiology*; D014867:Water / Q000378:metabolism*; D003313:Zea mays / Q000254:growth & development / Q000382:microbiology / Q000502:physiology*
chemical_list: D020346:Aquaporins; D008086:Lissamine Green Dyes; D010940:Plant Proteins; D012987:Soil; D014867:Water; C016537:Light green SF; D019810:Sodium Azide