title: The carbon bonus of organic nitrogen enhances nitrogen use efficiency of plants.
abstract: The importance of organic nitrogen (N) for plant nutrition and productivity is increasingly being recognized. Here we show that it is not only the availability in the soil that matters, but also the effects on plant growth. The chemical form of N taken up, whether inorganic (such as nitrate) or organic (such as amino acids), may significantly influence plant shoot and root growth, and nitrogen use efficiency (NUE). We analysed these effects by synthesizing results from multiple laboratory experiments on small seedlings (Arabidopsis, poplar, pine and spruce) based on a tractable plant growth model. A key point is that the carbon cost of assimilating organic N into proteins is lower than that of inorganic N, mainly because of its carbon content. This carbon bonus makes it more beneficial for plants to take up organic than inorganic N, even when its availability to the roots is much lower - up to 70% lower for Arabidopsis seedlings. At equal growth rate, root:shoot ratio was up to three times higher and nitrogen productivity up to 20% higher for organic than inorganic N, which both are factors that may contribute to higher NUE in crop production.
authors.affiliation: Ecosystems Services and Management Program, International Institute for Applied Systems Analysis, A-2361, Laxenburg, Austria.|Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-901 83, Umeå, Sweden.
authors.forename: Oskar
authors.initials: O
authors.lastname: Franklin
authors.affiliation: Department of Forest Genetics and Plant Physiology, Umeå Plant Science Centre, Swedish University of Agricultural Sciences, SE-901 85, Umeå, Sweden.
authors.forename: Camila Aguetoni
authors.initials: CA
authors.lastname: Cambui
authors.affiliation: Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-901 83, Umeå, Sweden.
authors.forename: Linda
authors.initials: L
authors.lastname: Gruffman
authors.affiliation: Nicholas School of the Environment and Earth Sciences, Duke University, Durham, NC, 27708, USA.
authors.forename: Sari
authors.initials: S
authors.lastname: Palmroth
authors.affiliation: Nicholas School of the Environment and Earth Sciences, Duke University, Durham, NC, 27708, USA.
authors.forename: Ram
authors.initials: R
authors.lastname: Oren
authors.affiliation: Department of Forest Genetics and Plant Physiology, Umeå Plant Science Centre, Swedish University of Agricultural Sciences, SE-901 85, Umeå, Sweden.|Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-901 83, Umeå, Sweden.
authors.forename: Torgny
authors.initials: T
authors.lastname: Näsholm
mesh_terms: D018533:Biomass; D002244:Carbon / Q000378:metabolism*; D008027:Light; D008954:Models, Biological; D009584:Nitrogen / Q000378:metabolism* / Q000494:pharmacology; D009930:Organic Chemicals / Q000378:metabolism*; D063245:Plant Development / Q000187:drug effects / Q000528:radiation effects; D018517:Plant Roots / Q000187:drug effects / Q000528:radiation effects; D018520:Plant Shoots / Q000187:drug effects / Q000528:radiation effects; D010944:Plants / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects
chemical_list: D009930:Organic Chemicals; D002244:Carbon; D009584:Nitrogen
keywords: allocation; amino acids; ammonium; assimilation; growth model; nitrate; nitrogen source; plant theory