title: Hormonal changes in relation to biomass partitioning and shoot growth impairment in salinized tomato (Solanum lycopersicum L.) plants.
abstract: Following exposure to salinity, the root/shoot ratio is increased (an important adaptive response) due to the rapid inhibition of shoot growth (which limits plant productivity) while root growth is maintained. Both processes may be regulated by changes in plant hormone concentrations. Tomato plants (Solanum lycopersicum L. cv Moneymaker) were cultivated hydroponically for 3 weeks under high salinity (100 mM NaCl) and five major plant hormones (abscisic acid, ABA; the cytokinins zeatin, Z, and zeatin-riboside, ZR; the auxin indole-3-acetic acid, IAA; and the ethylene precursor 1-aminocyclopropane-1-carboxylic acid, ACC) were determined weekly in roots, xylem sap, and leaves. Salinity reduced shoot biomass by 50-60% and photosynthetic area by 20-25% both by decreasing leaf expansion and delaying leaf appearance, while root growth was less affected, thus increasing the root/shoot ratio. ABA and ACC concentrations strongly increased in roots, xylem sap, and leaves after 1 d (ABA) and 15 d (ACC) of salinization. By contrast, cytokinins and IAA were differentially affected in roots and shoots. Salinity dramatically decreased the Z+ZR content of the plant, and induced the conversion of ZR into Z, especially in the roots, which accounted for the relative increase of cytokinins in the roots compared to the leaf. IAA concentration was also strongly decreased in the leaves while it accumulated in the roots. Decreased cytokinin content and its transport from the root to the shoot were probably induced by the basipetal transport of auxin from the shoot to the root. The auxin/cytokinin ratio in the leaves and roots may explain both the salinity-induced decrease in shoot vigour (leaf growth and leaf number) and the shift in biomass allocation to the roots, in agreement with changes in the activity of the sink-related enzyme cell wall invertase.
authors.affiliation: Departamento de Nutrición Vegetal, Centro de Edafología y Biología Aplicada del Segura (CEBAS), Consejo Superior de Investigaciones Científicas (CSIC), Campus Universitario de Espinardo, E-30100, Espinardo, Murcia, Spain.
authors.forename: Alfonso
authors.initials: A
authors.lastname: Albacete
authors.forename: Michel Edmond
authors.initials: ME
authors.lastname: Ghanem
authors.forename: Cristina
authors.initials: C
authors.lastname: Martínez-Andújar
authors.forename: Manuel
authors.initials: M
authors.lastname: Acosta
authors.forename: José
authors.initials: J
authors.lastname: Sánchez-Bravo
authors.forename: Vicente
authors.initials: V
authors.lastname: Martínez
authors.forename: Stanley
authors.initials: S
authors.lastname: Lutts
authors.forename: Ian C
authors.initials: IC
authors.lastname: Dodd
authors.forename: Francisco
authors.initials: F
authors.lastname: Pérez-Alfocea
mesh_terms: D001692:Biological Transport; D018533:Biomass; D018551:Solanum lycopersicum / Q000254:growth & development* / Q000378:metabolism; D010937:Plant Growth Regulators / Q000378:metabolism*; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism; D018520:Plant Shoots / Q000254:growth & development* / Q000378:metabolism; D012965:Sodium Chloride / Q000378:metabolism*
chemical_list: D010937:Plant Growth Regulators; D012965:Sodium Chloride