title: Ion transport in broad bean leaf mesophyll under saline conditions.
abstract: Salt stress reduces the ability of mesophyll tissue to respond to light. Potassium outward rectifying channels are responsible for 84 % of Na (+) induced potassium efflux from mesophyll cells. Modulation in ion transport of broad bean (Vicia faba L.) mesophyll to light under increased apoplastic salinity stress was investigated using vibrating ion-selective microelectrodes (the MIFE technique). Increased apoplastic Na(+) significantly affected mesophyll cells ability to respond to light by modulating ion transport across their membranes. Elevated apoplastic Na(+) also induced a significant K(+) efflux from mesophyll tissue. This efflux was mediated predominately by potassium outward rectifying channels (84 %) and the remainder of the efflux was through non-selective cation channels. NaCl treatment resulted in a reduction in photosystem II efficiency in a dose- and time-dependent manner. In particular, reductions in Fv'/Fm' were linked to K(+) homeostasis in the mesophyll tissue. Increased apoplastic Na(+) concentrations induced vanadate-sensitive net H(+) efflux, presumably mediated by the plasma membrane H(+)-ATPase. It is concluded that the observed pump's activation is essential for the maintenance of membrane potential and ion homeostasis in the cytoplasm of mesophyll under salt stress.
authors.affiliation: School of Land and Food, University of Tasmania, Private Bag 54, Hobart, TAS, 7001, Australia.
authors.forename: William J
authors.initials: WJ
authors.lastname: Percey
authors.forename: Lana
authors.initials: L
authors.lastname: Shabala
authors.forename: Michael C
authors.initials: MC
authors.lastname: Breadmore
authors.forename: Rosanne M
authors.initials: RM
authors.lastname: Guijt
authors.forename: Jayakumar
authors.initials: J
authors.lastname: Bose
authors.forename: Sergey
authors.initials: S
authors.lastname: Shabala
mesh_terms: D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D006706:Homeostasis / Q000187:drug effects; D017136:Ion Transport / Q000187:drug effects*; D008564:Membrane Potentials / Q000187:drug effects; D058503:Mesophyll Cells / Q000187:drug effects / Q000378:metabolism; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism; D010940:Plant Proteins / Q000187:drug effects / Q000378:metabolism; D011188:Potassium / Q000378:metabolism*; D006180:Proton-Translocating ATPases / Q000187:drug effects / Q000378:metabolism; D054712:Salinity; D012965:Sodium Chloride / Q000494:pharmacology*; D031307:Vicia faba / Q000187:drug effects / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D012965:Sodium Chloride; D006180:Proton-Translocating ATPases; D011188:Potassium