Ammonia production and assimilation: its importance as a tolerance mechanism during moderate water deficit in tomato plants |
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Authors: | Sánchez-Rodríguez Eva Rubio-Wilhelmi María del Mar Ríos Juan José Blasco Begoña Rosales Miguel Ángel Melgarejo Rubén Romero Luis Ruiz Juan Manuel |
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Affiliation: | Department of Plant Physiology, Faculty of Science, University of Granada, 18071 Granada, Spain |
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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. |
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Keywords: | AAT, aspartate aminotransferase GDH, glutamate dehydrogenase GGAT, glutamate: glyoxylate aminotransferase GO, glyoxylate oxidase GOGAT, glutamate synthase GS, glutamine synthetase HR, hydroxypyruvate reductase LRWC, leaf relative water content N, nitrogen NH4+, ammonia NO2-, nitrite NO3-, nitrate NR, nitrate reductase NiR, nitrite reductase 2-PG, glycolate-2-phosphate 3-PG, glycerate-3-phosphate RGR, relative growth rate ROS, reactive oxygen species RUBP, ribulose-1,5-biphosphate Rubisco, RUBP carboxylase/oxigenase SGAT, serine: glyoxylate aminotransferase |
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