title: Changes in intracellular and apoplastic peroxidase activity, ascorbate redox status, and root elongation induced by enhanced ascorbate content in Allium cepa L.
abstract: Onions (Allium cepa L.) treated with external ascorbic acid or with the immediate precursor of its synthesis L-galactono-gamma-lactone show a stimulated elongation rate of the roots and an increase in the number of new radicles appearing at the bulb base. Treatment with both molecules resulted in an enhanced accumulation of ascorbate and dehydroascorbate along the root axis, but the distribution of these redox forms was not uniform along the root, as detected in intracellular (symplastic) and extracellular (apoplastic) compartments. Thus, those radicular zones metabolically more active, such as the meristem and the elongation zone, accumulated the highest amount of both redox forms of ascorbate. On the other hand, ascorbate and L-galactono-gamma-lactone also stimulated cytosolic glucose-6-phosphate dehydrogenase activity and inhibited peroxidase activity as deduced from in vivo and in vitro experiments. Differences were also found when comparing apoplastic and symplastic activities. These results are compatible with the idea of an ascorbate-mediated stimulation of root growth by inhibiting cell wall stiffening and increasing root metabolism.
authors.affiliation: Departamento de Biología Celular, Fisiología e Inmunología, Universidad de Córdoba, Campus de Rabanales, Edificio Severo Ochoa, Planta 3, 14014 Córdoba, Spain.
authors.forename: María del Carmen
authors.initials: Mdel C
authors.lastname: Córdoba-Pedregosa
authors.forename: José Manuel
authors.initials: JM
authors.lastname: Villalba
authors.forename: Francisco
authors.initials: F
authors.lastname: Córdoba
authors.forename: José Antonio
authors.initials: JA
authors.lastname: González-Reyes
mesh_terms: D001205:Ascorbic Acid / Q000378:metabolism* / Q000494:pharmacology* / Q000502:physiology; D003683:Dehydroascorbic Acid / Q000378:metabolism; D005954:Glucosephosphate Dehydrogenase / Q000378:metabolism; D019697:Onions / Q000254:growth & development / Q000378:metabolism*; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000378:metabolism*; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism*; D013400:Sugar Acids / Q000494:pharmacology
chemical_list: D013400:Sugar Acids; C007813:galactonolactone; D005954:Glucosephosphate Dehydrogenase; D010544:Peroxidases; D001205:Ascorbic Acid; D003683:Dehydroascorbic Acid