title: Aluminum-dependent dynamics of ion transport in Arabidopsis: specificity of low pH and aluminum responses.
abstract: Low-pH and Al(3+) stresses are the major causes of poor plant growth in acidic soils. However, there is still a poor understanding of plant responses to low-pH and Al(3+) toxicity. Low-pH or combined low-pH and Al(3+) stress was imposed in order to measure rhizosphere pH, ion fluxes, plasma membrane potential and intracellular H(+) concentration in distal elongation and mature zones (MZs) along the longitudinal axis of Arabidopsis thaliana roots. Low-pH stress facilitated H(+) influx into root tissues and caused cytoplasmic acidification; by contrast, combined low-pH/Al(3+) treatment either decreased H(+) influx in the distal elongation zone (DEZ) or induced H(+) efflux in the MZ, leading to cytoplasmic alkalinization in both zones. Low-pH stress induced an increase in rhizosphere pH in the DEZ, whereas combined low-pH/Al(3+) stress resulted in lower rhizosphere pH in both root zones compared with the low-pH treatment alone. Low-pH stress facilitated K(+) efflux; the presence of Al(3+) diminished K(+) efflux or favored K(+) influx into root tissues. In both zones, low-pH treatment induced plasma membrane (PM) depolarization, which was significantly diminished (P<or= 0.05) when combined stresses (low-pH/100 microM Al(3+)) were imposed. After 60 min of exposure, low pH caused PM depolarization, whereas low pH/100 microM Al(3+) caused PM hyperpolarization. Thus, low pH and Al(3+) toxicity differentially affect root tissues and, consequently, the rhizosphere, which might underpin the differential mechanisms of plant adaptation to these abiotic stresses.
authors.affiliation: School of Earth and Environment, The University of Western Australia, Crawley, WA 6009, Australia.
authors.forename: Jayakumar
authors.initials: J
authors.lastname: Bose
authors.forename: Olga
authors.initials: O
authors.lastname: Babourina
authors.forename: Sergey
authors.initials: S
authors.lastname: Shabala
authors.forename: Zed
authors.initials: Z
authors.lastname: Rengel
mesh_terms: D000535:Aluminum / Q000378:metabolism*; D017360:Arabidopsis / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D017136:Ion Transport; D008564:Membrane Potentials; D018517:Plant Roots / Q000254:growth & development* / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D012987:Soil / Q000032:analysis
chemical_list: D012987:Soil; D000535:Aluminum; D011188:Potassium