title: Impact of atmospheric CO2 on growth, photosynthesis and nitrogen metabolism in cucumber (Cucumis sativus L.) plants.
abstract: Expression and activity of nitrate reductase (NR; EC 1.6.6.1) and glutamine synthetase (GS; EC 6.3.1.2) were analysed in relation to the rate of CO(2) assimilation in cucumber (Cucumis sativus L.) leaves. Intact plants were exposed to different atmospheric CO(2) concentrations (100, 400 and 1200microLL(-1)) for 14 days. A correlation between the in vivo rates of net CO(2) assimilation and the atmospheric CO(2) concentrations was observed. Transpiration rate and stomatal conductance remained unaffected by CO(2) levels. The exposure of the cucumber plants to rising CO(2) concentrations led to a concomitant increase in the contents of starch and soluble sugars, and a decrease in the nitrate content in leaves. At very low CO(2), NR and GS expression decreased, in spite of high nitrate contents, whereas at normal and elevated CO(2) expression and activity were high although the nitrate content was very low. Thus, in cucumber, NR and GS expression appear to be dominated by sugar levels, rather than by nitrate contents.
authors.affiliation: Departamento de Biología Vegetal, Area de Fisiología Vegetal, Facultad de Ciencias, Universidad de Córdoba, Campus de Rabanales, Edificio Celestino Mutis (C4), E-14071 Córdoba, Spain. bv1cahap@uco.es
authors.forename: Eloísa
authors.initials: E
authors.lastname: Agüera
authors.forename: David
authors.initials: D
authors.lastname: Ruano
authors.forename: Purificación
authors.initials: P
authors.lastname: Cabello
authors.forename: Purificación
authors.initials: P
authors.lastname: de la Haba
mesh_terms: D050260:Carbohydrate Metabolism; D002245:Carbon Dioxide / Q000378:metabolism*; D018553:Cucumis sativus / Q000254:growth & development* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D005974:Glutamate-Ammonia Ligase / Q000235:genetics / Q000378:metabolism; D050901:Nitrate Reductase / Q000235:genetics / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D010788:Photosynthesis / Q000502:physiology*; D010860:Pigments, Biological / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018526:Plant Transpiration / Q000502:physiology
chemical_list: D009566:Nitrates; D010860:Pigments, Biological; D010940:Plant Proteins; D002245:Carbon Dioxide; D050901:Nitrate Reductase; D005974:Glutamate-Ammonia Ligase; D009584:Nitrogen