title: Ammonia production and assimilation: its importance as a tolerance mechanism during moderate water deficit in tomato plants.
abstract: Nitrate assimilation diminishes under water stress. This can augment the photorespiratory rate as a protection mechanism, increasing the ammonium concentration, which must be rapidly assimilated. We therefore examined the effect of moderate water stress in photorespiration and N assimilation, as possible tolerance mechanisms in cherry tomato. Five cherry tomato cultivars with different degrees of water stress tolerance were submitted to two water treatments: well-watered (100% FC) and water stress (50% FC). In the susceptible cultivars, nitrate assimilation declined but without stimulating photorespiration. Zarina, a stress-tolerant cultivar, showed increased activity of the main enzymes involved in photorespiration, together with greater assimilation of nitrates and of the resulting ammonium. This translates as higher concentrations of N as well as amino acids and proteins. We characterize these mechanisms in the cv. Zarina (tolerant) as essential to water stress tolerance, acting on N metabolism as well as helping to maintain or augment biomass.
authors.affiliation: Department of Plant Physiology, Faculty of Science, University of Granada, 18071 Granada, Spain. evasr@ugr.es
authors.forename: Eva
authors.initials: E
authors.lastname: Sánchez-Rodríguez
authors.forename: María del Mar
authors.initials: Mdel M
authors.lastname: Rubio-Wilhelmi
authors.forename: Juan José
authors.initials: JJ
authors.lastname: Ríos
authors.forename: Begoña
authors.initials: B
authors.lastname: Blasco
authors.forename: Miguel Ángel
authors.initials: MÁ
authors.lastname: Rosales
authors.forename: Rubén
authors.initials: R
authors.lastname: Melgarejo
authors.forename: Luis
authors.initials: L
authors.lastname: Romero
authors.forename: Juan Manuel
authors.initials: JM
authors.lastname: Ruiz
mesh_terms: D000222:Adaptation, Physiological; D000596:Amino Acids / Q000378:metabolism; D000641:Ammonia / Q000032:analysis / Q000378:metabolism*; D018533:Biomass; D019069:Cell Respiration / Q000502:physiology; D003681:Dehydration / Q000378:metabolism; D055864:Droughts; D018551:Solanum lycopersicum / Q000378:metabolism / Q000502:physiology*; D050901:Nitrate Reductase / Q000235:genetics / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D013312:Stress, Physiological
chemical_list: D000596:Amino Acids; D009566:Nitrates; D010940:Plant Proteins; D000641:Ammonia; D050901:Nitrate Reductase; D009584:Nitrogen