title: Nitrogen use strategies of seedlings from neotropical tree species of distinct successional groups.
abstract: Few studies have analyzed the strategies of neotropical tree seedlings for absorbing, translocating and assimilating the nitrogen. Here, we compared the nitrogen use strategies of seedlings from six tree species that are native to the Brazilian Atlantic Forest and that belong to different successional groups: Trema micrantha, Heliocarpus popayanensis and Cecropia pachystachya (pioneers), Cariniana estrellensis, Eugenia brasiliensis and Guarea kunthiana (non-pioneers). The effects of cultivating seedlings with nitrate or ammonium on the growth, physiology and nitrogen metabolism were analyzed. Nitrate-grown pioneer species had much higher leaf nitrate reductase activity than non-pioneer ones, but non-pioneer seedlings were also able to use nitrate as a nitrogen source. In addition to this remarkable difference between the groups in the capacity for leaf nitrate assimilation, substantial variations in the nitrogen use strategies were observed within the successional classes. Differently from the other non-pioneers, the canopy species C. estrellensis seemed to assimilate nitrate mainly in the leaves. Morphophysiological analyses showed a gradient of ammonium toxicity response, with E. brasiliensis as the most tolerant species, and T. micrantha and H. popayanensis as the most sensitive ones. Guarea kunthiana showed a relatively low tolerance to ammonium and an unusual high translocation of this cation in the xylem sap. In contrast to the other pioneers, C. pachystachya had a high plasticity in the use of nitrogen sources. Overall, these results suggest that nitrogen use strategies of neotropical tree seedlings were not determined solely by their successional position.
authors.affiliation: Department of Animal and Plant Biology, UEL - University of Londrina, Londrina, PR, Brazil. Electronic address: halley@uel.br.
authors.forename: Halley Caixeta
authors.initials: HC
authors.lastname: Oliveira
authors.affiliation: Department of Animal and Plant Biology, UEL - University of Londrina, Londrina, PR, Brazil.
authors.forename: Ligia Maria Inocêncio
authors.initials: LM
authors.lastname: da Silva
authors.affiliation: Department of Animal and Plant Biology, UEL - University of Londrina, Londrina, PR, Brazil.
authors.forename: Letícia Dias
authors.initials: LD
authors.lastname: de Freitas
authors.affiliation: Department of Animal and Plant Biology, UEL - University of Londrina, Londrina, PR, Brazil.
authors.forename: Tatiane Viegas
authors.initials: TV
authors.lastname: Debiasi
authors.affiliation: Plant Physiology and Biochemistry Section, Institute of Botany, São Paulo, SP, Brazil.
authors.forename: Nidia Mara
authors.initials: NM
authors.lastname: Marchiori
authors.affiliation: Plant Physiology and Biochemistry Section, Institute of Botany, São Paulo, SP, Brazil.
authors.forename: Marcos Pereira Marinho
authors.initials: MP
authors.lastname: Aidar
authors.affiliation: Department of Animal and Plant Biology, UEL - University of Londrina, Londrina, PR, Brazil.
authors.forename: Edmilson
authors.initials: E
authors.lastname: Bianchini
authors.affiliation: Department of Animal and Plant Biology, UEL - University of Londrina, Londrina, PR, Brazil.
authors.forename: José Antonio
authors.initials: JA
authors.lastname: Pimenta
authors.affiliation: Department of Animal and Plant Biology, UEL - University of Londrina, Londrina, PR, Brazil.
authors.forename: Renata
authors.initials: R
authors.lastname: Stolf-Moreira
mesh_terms: D064751:Ammonium Compounds / Q000378:metabolism; D001692:Biological Transport; D001938:Brazil; D002980:Climate; D017753:Ecosystem; D050901:Nitrate Reductase / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D018517:Plant Roots / Q000378:metabolism; D036226:Seedlings / Q000378:metabolism* / Q000502:physiology; D014197:Trees / Q000378:metabolism*; D052584:Xylem / Q000378:metabolism
chemical_list: D064751:Ammonium Compounds; D010940:Plant Proteins; D050901:Nitrate Reductase; D009584:Nitrogen
keywords: Ammonium; Ammonium toxicity; Nitrate; Nitrate reductase; Nitrogen metabolism; Plant sucession