title: Abscisic Acid Regulation of Root Hydraulic Conductivity and Aquaporin Gene Expression Is Crucial to the Plant Shoot Growth Enhancement Caused by Rhizosphere Humic Acids.
abstract: The physiological and metabolic mechanisms behind the humic acid-mediated plant growth enhancement are discussed in detail. Experiments using cucumber (Cucumis sativus) plants show that the shoot growth enhancement caused by a structurally well-characterized humic acid with sedimentary origin is functionally associated with significant increases in abscisic acid (ABA) root concentration and root hydraulic conductivity. Complementary experiments involving a blocking agent of cell wall pores and water root transport (polyethylenglycol) show that increases in root hydraulic conductivity are essential in the shoot growth-promoting action of the model humic acid. Further experiments involving an inhibitor of ABA biosynthesis in root and shoot (fluridone) show that the humic acid-mediated enhancement of both root hydraulic conductivity and shoot growth depended on ABA signaling pathways. These experiments also show that a significant increase in the gene expression of the main root plasma membrane aquaporins is associated with the increase of root hydraulic conductivity caused by the model humic acid. Finally, experimental data suggest that all of these actions of model humic acid on root functionality, which are linked to its beneficial action on plant shoot growth, are likely related to the conformational structure of humic acid in solution and its interaction with the cell wall at the root surface.
authors.affiliation: Department of Environmental Biology (Agricultural Chemistry and Biology Group), Faculty of Sciences, University of Navarra, 31080 Pamplona, Spain (M.O., V.M., E.B., M.G., M.F., E.C., A.M.Z., R.B., J.M.G.-M.); andAntenna Group, Electrical and Electronic Engineering Department, Public University of Navarra, 31006 Pamplona, Spain (J.C.I., D.E., I.E., R.G.).
authors.forename: Maite
authors.identifier: http://orcid.org/0000-0001-9858-4910
authors.initials: M
authors.lastname: Olaetxea
authors.affiliation: Department of Environmental Biology (Agricultural Chemistry and Biology Group), Faculty of Sciences, University of Navarra, 31080 Pamplona, Spain (M.O., V.M., E.B., M.G., M.F., E.C., A.M.Z., R.B., J.M.G.-M.); andAntenna Group, Electrical and Electronic Engineering Department, Public University of Navarra, 31006 Pamplona, Spain (J.C.I., D.E., I.E., R.G.).
authors.forename: Verónica
authors.identifier: http://orcid.org/0000-0001-8255-4792
authors.initials: V
authors.lastname: Mora
authors.affiliation: Department of Environmental Biology (Agricultural Chemistry and Biology Group), Faculty of Sciences, University of Navarra, 31080 Pamplona, Spain (M.O., V.M., E.B., M.G., M.F., E.C., A.M.Z., R.B., J.M.G.-M.); andAntenna Group, Electrical and Electronic Engineering Department, Public University of Navarra, 31006 Pamplona, Spain (J.C.I., D.E., I.E., R.G.).
authors.forename: Eva
authors.initials: E
authors.lastname: Bacaicoa
authors.affiliation: Department of Environmental Biology (Agricultural Chemistry and Biology Group), Faculty of Sciences, University of Navarra, 31080 Pamplona, Spain (M.O., V.M., E.B., M.G., M.F., E.C., A.M.Z., R.B., J.M.G.-M.); andAntenna Group, Electrical and Electronic Engineering Department, Public University of Navarra, 31006 Pamplona, Spain (J.C.I., D.E., I.E., R.G.).
authors.forename: María
authors.initials: M
authors.lastname: Garnica
authors.affiliation: Department of Environmental Biology (Agricultural Chemistry and Biology Group), Faculty of Sciences, University of Navarra, 31080 Pamplona, Spain (M.O., V.M., E.B., M.G., M.F., E.C., A.M.Z., R.B., J.M.G.-M.); andAntenna Group, Electrical and Electronic Engineering Department, Public University of Navarra, 31006 Pamplona, Spain (J.C.I., D.E., I.E., R.G.).
authors.forename: Marta
authors.initials: M
authors.lastname: Fuentes
authors.affiliation: Department of Environmental Biology (Agricultural Chemistry and Biology Group), Faculty of Sciences, University of Navarra, 31080 Pamplona, Spain (M.O., V.M., E.B., M.G., M.F., E.C., A.M.Z., R.B., J.M.G.-M.); andAntenna Group, Electrical and Electronic Engineering Department, Public University of Navarra, 31006 Pamplona, Spain (J.C.I., D.E., I.E., R.G.).
authors.forename: Esther
authors.initials: E
authors.lastname: Casanova
authors.affiliation: Department of Environmental Biology (Agricultural Chemistry and Biology Group), Faculty of Sciences, University of Navarra, 31080 Pamplona, Spain (M.O., V.M., E.B., M.G., M.F., E.C., A.M.Z., R.B., J.M.G.-M.); andAntenna Group, Electrical and Electronic Engineering Department, Public University of Navarra, 31006 Pamplona, Spain (J.C.I., D.E., I.E., R.G.).
authors.forename: Angel M
authors.identifier: http://orcid.org/0000-0003-1966-0239
authors.initials: AM
authors.lastname: Zamarreño
authors.affiliation: Department of Environmental Biology (Agricultural Chemistry and Biology Group), Faculty of Sciences, University of Navarra, 31080 Pamplona, Spain (M.O., V.M., E.B., M.G., M.F., E.C., A.M.Z., R.B., J.M.G.-M.); andAntenna Group, Electrical and Electronic Engineering Department, Public University of Navarra, 31006 Pamplona, Spain (J.C.I., D.E., I.E., R.G.).
authors.forename: Juan C
authors.identifier: http://orcid.org/0000-0002-2860-5138
authors.initials: JC
authors.lastname: Iriarte
authors.affiliation: Department of Environmental Biology (Agricultural Chemistry and Biology Group), Faculty of Sciences, University of Navarra, 31080 Pamplona, Spain (M.O., V.M., E.B., M.G., M.F., E.C., A.M.Z., R.B., J.M.G.-M.); andAntenna Group, Electrical and Electronic Engineering Department, Public University of Navarra, 31006 Pamplona, Spain (J.C.I., D.E., I.E., R.G.).
authors.forename: David
authors.initials: D
authors.lastname: Etayo
authors.affiliation: Department of Environmental Biology (Agricultural Chemistry and Biology Group), Faculty of Sciences, University of Navarra, 31080 Pamplona, Spain (M.O., V.M., E.B., M.G., M.F., E.C., A.M.Z., R.B., J.M.G.-M.); andAntenna Group, Electrical and Electronic Engineering Department, Public University of Navarra, 31006 Pamplona, Spain (J.C.I., D.E., I.E., R.G.).
authors.forename: Iñigo
authors.initials: I
authors.lastname: Ederra
authors.affiliation: Department of Environmental Biology (Agricultural Chemistry and Biology Group), Faculty of Sciences, University of Navarra, 31080 Pamplona, Spain (M.O., V.M., E.B., M.G., M.F., E.C., A.M.Z., R.B., J.M.G.-M.); andAntenna Group, Electrical and Electronic Engineering Department, Public University of Navarra, 31006 Pamplona, Spain (J.C.I., D.E., I.E., R.G.).
authors.forename: Ramón
authors.initials: R
authors.lastname: Gonzalo
authors.affiliation: Department of Environmental Biology (Agricultural Chemistry and Biology Group), Faculty of Sciences, University of Navarra, 31080 Pamplona, Spain (M.O., V.M., E.B., M.G., M.F., E.C., A.M.Z., R.B., J.M.G.-M.); andAntenna Group, Electrical and Electronic Engineering Department, Public University of Navarra, 31006 Pamplona, Spain (J.C.I., D.E., I.E., R.G.) rbaigorri@timacagro.es jgmina@unav.es.
authors.forename: Roberto
authors.identifier: http://orcid.org/0000-0002-9197-5895
authors.initials: R
authors.lastname: Baigorri
authors.affiliation: Department of Environmental Biology (Agricultural Chemistry and Biology Group), Faculty of Sciences, University of Navarra, 31080 Pamplona, Spain (M.O., V.M., E.B., M.G., M.F., E.C., A.M.Z., R.B., J.M.G.-M.); andAntenna Group, Electrical and Electronic Engineering Department, Public University of Navarra, 31006 Pamplona, Spain (J.C.I., D.E., I.E., R.G.) rbaigorri@timacagro.es jgmina@unav.es.
authors.forename: Jose M
authors.identifier: http://orcid.org/0000-0001-6352-9612
authors.initials: JM
authors.lastname: García-Mina
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D020346:Aquaporins / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport; D018553:Cucumis sativus / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D006812:Humic Substances; D010937:Plant Growth Regulators / Q000378:metabolism*; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D018520:Plant Shoots / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D018526:Plant Transpiration; D058441:Rhizosphere; D014867:Water / Q000378:metabolism
chemical_list: D020346:Aquaporins; D006812:Humic Substances; D010937:Plant Growth Regulators; D014867:Water; D000040:Abscisic Acid