title: Nitrate concentration effects on NO3-N uptake and reduction, growth, and fruit yield in strawberry.
abstract: Strawberries (Fragaria xananassa Duch. 'Osogrande') were grown hydroponically with three NO3-N concentrations (3.75, 7.5, or 15.0 mM) to determine effects of varying concentration on NO3-N uptake and reduction rates, and to relate these processes to growth and fruit yield. Plants were grown for 32 weeks, and NO3-N uptake and nitrate reductase (NR) activities in roots and shoots were measured during vegetative and reproductive growth. In general, NO3-N uptake rates increased as NO3-N concentration in the hydroponics system increased. Tissue NO3- concentration also increased as external NO3-N concentration increased, reflecting the differences in uptake rates. There was no effect of external NO3-N concentration on NR activities in leaves or roots during either stage of development. Leaf NR activity averaged approximately 360 nmol NO2 formed/g fresh weight (FW)/h over both developmental stages, while NR activity in roots was much lower, averaging approximately 115 nmol NO2 formed/g FW/h. Vegetative organ FW, dry weight (DW), and total fruit yield were unaffected by NO3-N concentration. These data suggest that the inability of strawberry to increase growth and fruit yield in response to increasing NO3-N concentrations is not due to limitations in NO3-N uptake rates, but rather to limitations in NO3- reduction and/or assimilation in both roots and leaves.
authors.affiliation: Horticultural Sciences Department, University of Florida, Gainesville, FL 32611-0690, USA.
authors.forename: R L
authors.initials: RL
authors.lastname: Darnell
authors.forename: G W
authors.initials: GW
authors.lastname: Stutte
mesh_terms: D003470:Culture Media / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005638:Fruit / Q000201:enzymology / Q000254:growth & development* / Q000378:metabolism; D018527:Hydroponics; D050901:Nitrate Reductase; D009565:Nitrate Reductases / Q000378:metabolism*; D009566:Nitrates / Q000378:metabolism / Q000493:pharmacokinetics*; D009584:Nitrogen / Q000378:metabolism / Q000493:pharmacokinetics*; D018515:Plant Leaves / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism; D018517:Plant Roots / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism; D027824:Rosaceae / Q000201:enzymology / Q000254:growth & development* / Q000378:metabolism*
chemical_list: D003470:Culture Media; D009566:Nitrates; D009565:Nitrate Reductases; D050901:Nitrate Reductase; D009584:Nitrogen