title: Nitrogen balance for wheat canopies (Triticum aestivum cv. Veery 10) grown under elevated and ambient CO2 concentrations.
abstract: We examined the hypothesis that elevated CO2 concentration would increase NO3- absorption and assimilation using intact wheat canopies (Triticum aestivum cv. Veery 10). Nitrate consumption, the sum of plant absorption and nitrogen loss, was continuously monitored for 23 d following germination under two CO2 concentrations (360 and 1000 micromol mol-1 CO2) and two root zone NO3- concentrations (100 and 1000 mmol m3 NO3-). The plants were grown at high density (1780 m-2) in a 28 m3 controlled environment chamber using solution culture techniques. Wheat responded to 1000 micromol mol-1 CO2 by increasing carbon allocation to root biomass production. Elevated CO2 also increased root zone NO3- consumption, but most of this increase did not result in higher biomass nitrogen. Rather, nitrogen loss accounted for the greatest part of the difference in NO3- consumption between the elevated and ambient [CO2] treatments. The total amount of NO3(-)-N absorbed by roots or the amount of NO3(-)-N assimilated per unit area did not significantly differ between elevated and ambient [CO2] treatments. Instead, specific leaf organic nitrogen content declined, and NO3- accumulated in canopies growing under 1000 micromol mol-1 CO2. Our results indicated that 1000 micromol mol-1 CO2 diminished NO3- assimilation. If NO3- assimilation were impaired by high [CO2], then this offers an explanation for why organic nitrogen contents are often observed to decline in elevated [CO2] environments.
authors.affiliation: Department of Vegetable Crops, University of California, Davis 95616-8746, USA. drsmart@vegmail.ucdavis.edu
authors.forename: D R
authors.initials: DR
authors.lastname: Smart
authors.forename: K
authors.initials: K
authors.lastname: Ritchie
authors.forename: A J
authors.initials: AJ
authors.lastname: Bloom
authors.forename: B B
authors.initials: BB
authors.lastname: Bugbee
mesh_terms: D000042:Absorption / Q000187:drug effects; D018533:Biomass; D002245:Carbon Dioxide / Q000494:pharmacology*; D004780:Environment, Controlled; D009566:Nitrates / Q000378:metabolism / Q000493:pharmacokinetics*; D009584:Nitrogen / Q000378:metabolism* / Q000493:pharmacokinetics; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D018520:Plant Shoots / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D018526:Plant Transpiration; D014908:Triticum / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism*
chemical_list: D009566:Nitrates; D002245:Carbon Dioxide; D009584:Nitrogen