title: Early changes of the pH of the apoplast are different in leaves, stem and roots of Vicia faba L. under declining water availability.
abstract: Changes in pH of the apoplast have recently been discussed as an important factor in adjusting transpiration and water relations under conditions of drought via modulatory effect on abscisic acid (ABA) concentration. Using Vicia faba L., we investigated whether changes in the root, shoot and leaf apoplastic pH correlated with (1) a drought-induced reduction in transpiration and with (2) changes in ABA concentration. Transpiration, leaf water potential and ABA in leaves were measured and correlated with root and shoot xylem pH, determined by a pH microelectrode, and pH of leaf apoplast quantified by microscopy-based in vivo ratiometric analysis. Results revealed that a reduction in transpiration rate in the early phase of soil drying could not be linked with changes in the apoplastic pH via effects on the stomata-regulating hormone ABA. Moreover, drought-induced increase in pH of xylem or leaf apoplast was not the remote effect of an acropetal transport of alkaline sap from root, because root xylem acidified during progressive soil drying, whereas the shoot apoplast alkalized. We reason that other, yet unknown signalling mechanism was responsible for reduction of transpiration rate in the early phase of soil drying.
authors.affiliation: Department of Experimental Biology, Masaryk University, Brno, Czechia.
authors.forename: T
authors.initials: T
authors.lastname: Karuppanapandian
authors.affiliation: Institute of Plant Nutrition and Soil Science, Kiel University, Kiel, Germany; Institute of Crop Science, Division of Crop Product Quality, University of Hohenheim, Emil-Wolff-Straße 25, 70599 Stuttgart, Germany.
authors.forename: C-M
authors.initials: CM
authors.lastname: Geilfus
authors.affiliation: Institute of Plant Nutrition and Soil Science, Kiel University, Kiel, Germany.
authors.forename: K-H
authors.initials: KH
authors.lastname: Mühling
authors.affiliation: Laboratory of Growth Regulators, Palacký University & Institute of Experimental Botany Academy of Sciences of the Czech Republic, Olomouc, Czechia.
authors.forename: O
authors.initials: O
authors.lastname: Novák
authors.affiliation: Department of Experimental Biology, Masaryk University, Brno, Czechia. Electronic address: VitGloser@sci.muni.cz.
authors.forename: V
authors.initials: V
authors.lastname: Gloser
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D000222:Adaptation, Physiological; D001692:Biological Transport; D055864:Droughts; D006863:Hydrogen-Ion Concentration; D018515:Plant Leaves / Q000737:chemistry / Q000502:physiology; D018517:Plant Roots / Q000737:chemistry / Q000502:physiology; D018547:Plant Stems / Q000737:chemistry / Q000502:physiology; D054046:Plant Stomata; D018514:Plant Structures / Q000737:chemistry / Q000502:physiology*; D018526:Plant Transpiration / Q000502:physiology*; D012987:Soil; D013312:Stress, Physiological; D031307:Vicia faba / Q000737:chemistry / Q000502:physiology*; D014867:Water / Q000502:physiology*; D052584:Xylem / Q000737:chemistry
chemical_list: D012987:Soil; D014867:Water; D000040:Abscisic Acid
keywords: Abscisic acid; Drought stress; Leaf water potential; Osmolality; Soil drying; Water relations; Xylem sap