title: Influence of the temporal and spatial variation of nitrate reductase, glutamine synthetase and soil composition in the N species content in lettuce (Lactuca sativa).
abstract: The variation of nitrate reductase (NR), glutamine synthetase (GS) and N content in lettuce was evaluated at 5 stages of lettuce growth. Soil physicochemical properties and its N content were also assessed to elucidate the soil-to-plant transfer of inorganic N and potential leaching to groundwater. A decrease of NR activity and an increase of NO3(-) and N-Kjeldahl content in lettuces were observed during plant growth, whereas GS activity and NH4(+) increased during the first few weeks of lettuce growth and then decreased. Although the temporal variation was similar in lettuces grown in different soils, quantitative differences were observed, indicating that high NO3(-) content in soil caused a higher NO3(-) accumulation in lettuce despite the higher NR activity during the initial stage of plant growth. Higher levels of NO3(-) and NH4(+) were correlated with higher levels of N-Kjeldahl in lettuce suggesting a positive effect of these N species in the biosynthesis of organic forms of N. Soil physicochemical properties influenced the mobility of inorganic N within the groundwater-soil-plant system. Sandy soils with low OM content allowed NO3(-) leaching, which was confirmed by higher NO3(-) levels in groundwater. Therefore, lettuces grown in those soils presented lower N content and the inputs of N to the environment were higher.
authors.affiliation: REQUIMTE/Departamento de Ciências Químicas, Laboratório de Bromatologia e Hidrologia da Faculdade de Farmácia da Universidade do Porto, Portugal.
authors.forename: Edgar
authors.initials: E
authors.lastname: Pinto
authors.affiliation: BioFIG - Center for Biodiversity, Functional & Integrative Genomics, Departamento de Biologia, Faculdade de Ciências, Universidade do Porto, Portugal.
authors.forename: Fernanda
authors.initials: F
authors.lastname: Fidalgo
authors.affiliation: BioFIG - Center for Biodiversity, Functional & Integrative Genomics, Departamento de Biologia, Faculdade de Ciências, Universidade do Porto, Portugal.
authors.forename: Jorge
authors.initials: J
authors.lastname: Teixeira
authors.affiliation: REQUIMTE/Faculdade de Ciências da Universidade do Porto, Portugal.
authors.forename: Ana A
authors.initials: AA
authors.lastname: Aguiar
authors.affiliation: REQUIMTE/Departamento de Ciências Químicas, Laboratório de Bromatologia e Hidrologia da Faculdade de Farmácia da Universidade do Porto, Portugal. Electronic address: isabel.ferreira@ff.up.pt.
authors.forename: Isabel M P L V O
authors.initials: IM
authors.lastname: Ferreira
mesh_terms: D018533:Biomass; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism*; D018545:Lactuca / Q000201:enzymology* / Q000254:growth & development; D050901:Nitrate Reductase / Q000378:metabolism*; D009584:Nitrogen / Q000032:analysis / Q000378:metabolism; D017672:Nitrogen Compounds / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism*; D012987:Soil / Q000737:chemistry
chemical_list: D017672:Nitrogen Compounds; D010940:Plant Proteins; D012987:Soil; D050901:Nitrate Reductase; D005974:Glutamate-Ammonia Ligase; D009584:Nitrogen
keywords: Ammonium; Glutamine synthetase; Lactuca sativa; Nitrate; Nitrate reductase; Soil composition