title: Stomatal closure is induced by hydraulic signals and maintained by ABA in drought-stressed grapevine.
abstract: Water saving under drought stress is assured by stomatal closure driven by active (ABA-mediated) and/or passive (hydraulic-mediated) mechanisms. There is currently no comprehensive model nor any general consensus about the actual contribution and relative importance of each of the above factors in modulating stomatal closure in planta. In the present study, we assessed the contribution of passive (hydraulic) vs active (ABA mediated) mechanisms of stomatal closure in V. vinifera plants facing drought stress. Leaf gas exchange decreased progressively to zero during drought, and embolism-induced loss of hydraulic conductance in petioles peaked to ~50% in correspondence with strong daily limitation of stomatal conductance. Foliar ABA significantly increased only after complete stomatal closure had already occurred. Rewatering plants after complete stomatal closure and after foliar ABA reached maximum values did not induced stomatal re-opening, despite embolism recovery and water potential rise. Our data suggest that in grapevine stomatal conductance is primarily regulated by passive hydraulic mechanisms. Foliar ABA apparently limits leaf gas exchange over long-term, also preventing recovery of stomatal aperture upon rewatering, suggesting the occurrence of a mechanism of long-term down-regulation of transpiration to favor embolism repair and preserve water under conditions of fluctuating water availability and repeated drought events.
authors.affiliation: Dipartimento di Scienze Agrarie, Alimentari e Ambientali, University of Perugia, Borgo 20 giugno 74, 06121 Perugia, Italy.
authors.forename: Sergio
authors.initials: S
authors.lastname: Tombesi
authors.affiliation: Dipartimento di Scienze della Vita, University of Trieste, Via L. Giorgieri 10, 34127 Trieste, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Nardini
authors.affiliation: Dipartimento di Scienze Agrarie, Alimentari e Ambientali, University of Perugia, Borgo 20 giugno 74, 06121 Perugia, Italy.
authors.forename: Tommaso
authors.initials: T
authors.lastname: Frioni
authors.affiliation: Dipartimento di Scienze Agrarie, Alimentari e Ambientali, University of Perugia, Borgo 20 giugno 74, 06121 Perugia, Italy.
authors.forename: Marta
authors.initials: M
authors.lastname: Soccolini
authors.affiliation: Dipartimento di Scienze Farmaceutiche, University of Perugia, Borgo 20 giugno 74, 06121 Perugia, Italy.
authors.forename: Claudia
authors.initials: C
authors.lastname: Zadra
authors.affiliation: Dipartimento di Scienze Agrarie, Alimentari e Ambientali, University of Perugia, Borgo 20 giugno 74, 06121 Perugia, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Farinelli
authors.affiliation: Dipartimento di Scienze delle Produzioni Vegetali Sostenibili, Università Cattolica del Sacro Cuore, Via E. Parmense 84, 29100 Piacenza, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Poni
authors.affiliation: Dipartimento di Scienze Agrarie, Alimentari e Ambientali, University of Perugia, Borgo 20 giugno 74, 06121 Perugia, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Palliotti
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D000222:Adaptation, Physiological; D001692:Biological Transport; D055864:Droughts; D040542:Mechanotransduction, Cellular / Q000502:physiology; D010937:Plant Growth Regulators / Q000378:metabolism*; D054046:Plant Stomata / Q000187:drug effects / Q000502:physiology*; D018526:Plant Transpiration / Q000187:drug effects / Q000502:physiology*; D027843:Vitis / Q000187:drug effects / Q000502:physiology*; D014867:Water / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D010937:Plant Growth Regulators; D014867:Water; D000040:Abscisic Acid