title: Dynamics of exogenous nitrogen partitioning and nitrogen remobilization from vegetative organs in pea revealed by 15N in vivo labeling throughout seed filling.
abstract: The fluxes of (1) exogenous nitrogen (N) assimilation and (2) remobilization of endogenous N from vegetative plant compartments were measured by 15N labeling during the seed-filling period in pea (Pisum sativum L. cv Cameor), to better understand the mechanism of N remobilization. While the majority (86%) of exogenous N was allocated to the vegetative organs before the beginning of seed filling, this fraction decreased to 45% at the onset of seed filling, the remainder being directed to seeds. Nitrogen remobilization from vegetative parts contributed to 71% of the total N in mature seeds borne on the first two nodes (first stratum). The contribution of remobilized N to total seed N varied, with the highest proportion at the beginning of filling; it was independent of the developmental stage of each stratum of seeds, suggesting that remobilized N forms a unique pool, managed at the whole-plant level and supplied to all filling seeds whatever their position on the plant. Once seed filling starts, N is remobilized from all vegetative organs: 30% of the total N accumulated in seeds was remobilized from leaves, 20% from pod walls, 11% from roots, and 10% from stems. The rate of N remobilization was maximal when seeds of all the different strata were filling, consistent with regulation according to the N demand of seeds. At later stages of seed filling, the rate of remobilization decreases and may become controlled by the amount of residual N in vegetative tissues.
authors.affiliation: Unité de Génétique et d'Ecophysiologie des Légumineuses à Graines, Institut National de la Recherche Agronomique, 21065 Dijon cedex, France. schiltz@epoisses.inra.fr
authors.forename: Séverine
authors.initials: S
authors.lastname: Schiltz
authors.forename: Nathalie
authors.initials: N
authors.lastname: Munier-Jolain
authors.forename: Christian
authors.initials: C
authors.lastname: Jeudy
authors.forename: Judith
authors.initials: J
authors.lastname: Burstin
authors.forename: Christophe
authors.initials: C
authors.lastname: Salon
mesh_terms: D007700:Kinetics; D009584:Nitrogen / Q000378:metabolism*; D009587:Nitrogen Isotopes; D018532:Pisum sativum / Q000196:embryology* / Q000378:metabolism*; D012639:Seeds / Q000378:metabolism
chemical_list: D009587:Nitrogen Isotopes; D009584:Nitrogen