title: Changes in root hydraulic conductivity facilitate the overall hydraulic response of rice (Oryza sativa L.) cultivars to salt and osmotic stress.
abstract: The aim of the present work was to assess the significance of changes in root AQP gene expression and hydraulic conductivity (Lp) in the regulation of water balance in two hydroponically-grown rice cultivars (Azucena, Bala) which differ in root morphology, stomatal regulation and aquaporin (AQP) isoform expression. Plants were exposed to NaCl (25 mM, 50 mM) and osmotic stress (5%, 10% PEG6000). Root Lp was determined for exuding root systems (osmotic forces driving water uptake; 'exudation Lp') and transpiring plants (hydrostatic forces dominating; 'transpiration-Lp'). Gene expression was analysed by qPCR. Stress treatments caused a consistent and significant decrease in plant growth, transpirational water loss, stomatal conductance, shoot-to-root surface area ratio and root Lp. Comparison of exudation-with transpiration-Lp supported a significant contribution of AQP-facilitated water flow to root water uptake. Changes in root Lp in response to treatments were correlated much stronger with root morphological characteristics, such as the number of main and lateral roots, surface area ratio of root to shoot and plant transpiration rate than with AQP gene expression. Changes in root Lp, involving AQP function, form an integral part of the plant hydraulic response to stress and facilitate changes in the root-to-shoot surface area ratio, transpiration and stomatal conductance.
authors.affiliation: School of Biology and Environmental Sciences, University College Dublin (UCD), Belfield, Dublin 4, Republic of Ireland. Electronic address: Meng.Delong@ucdconnect.ie.
authors.forename: Delong
authors.initials: D
authors.lastname: Meng
authors.affiliation: School of Biology and Environmental Sciences, University College Dublin (UCD), Belfield, Dublin 4, Republic of Ireland. Electronic address: Wieland.fricke@ucd.ie.
authors.forename: Wieland
authors.initials: W
authors.lastname: Fricke
mesh_terms: D020346:Aquaporins / Q000378:metabolism; D001692:Biological Transport; D018527:Hydroponics; D012275:Oryza / Q000033:anatomy & histology / Q000378:metabolism*; D009997:Osmotic Pressure; D010940:Plant Proteins / Q000378:metabolism; D018517:Plant Roots / Q000033:anatomy & histology / Q000378:metabolism*; D018526:Plant Transpiration / Q000502:physiology; D011092:Polyethylene Glycols / Q000378:metabolism / Q000494:pharmacology; D012965:Sodium Chloride / Q000378:metabolism* / Q000494:pharmacology; D013312:Stress, Physiological / Q000502:physiology; D014867:Water / Q000378:metabolism
chemical_list: D020346:Aquaporins; D010940:Plant Proteins; D014867:Water; D011092:Polyethylene Glycols; D012965:Sodium Chloride
keywords: Aquaporin; Hydraulic conductivity; Osmotic stress; Polyethylene glycol (PEG); Rice (Oryza sativa L.); Root-to-shoot ratio; Salinity stress