Ammonia production and assimilation: Its importance as a tolerance mechanism during moderate water deficit in tomato plants

• Published in: Journal of plant physiology 2011-05, Vol.168 (8), p.816-823
• Main Authors: Sánchez-Rodríguez, Eva, Rubio-Wilhelmi, María del Mar, Ríos, Juan José, Blasco, Begoña, Rosales, Miguel Ángel, Melgarejo, Rubén, Romero, Luis, Ruiz, Juan Manuel
• Format: Article
• Language: English
• Subjects: Adaptation, Physiological; Amino acids; Amino Acids - metabolism; Ammonia; Ammonia - analysis; Ammonia - metabolism; Assimilation; Biological and medical sciences; Biomass; Cell Respiration - physiology; Cherries; Dehydration - metabolism; Droughts; Fundamental and applied biological sciences. Psychology; GS–GOGAT cycle; Lycopersicon esculentum - metabolism; Lycopersicon esculentum - physiology; Metabolism; Nitrate reductase; Nitrate Reductase - genetics; Nitrate Reductase - metabolism; Nitrates; Nitrates - metabolism; Nitrogen - metabolism; Nitrogen assimilation; Photorespiration; Plant Leaves - metabolism; Plant Leaves - physiology; Plant physiology and development; Plant Proteins - genetics; Plant Proteins - metabolism; Plants (organisms); Solanum lycopersicum L; Stress concentration; Stress, Physiological; Stresses; Tolerances; Water stress
• ISSN: 0176-1617; 1618-1328
• DOI: 10.1016/j.jplph.2010.11.018

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.