title: Leaf δ(15)N as a physiological indicator of the responsiveness of N2-fixing alfalfa plants to elevated [CO2], temperature and low water availability.
abstract: The natural (15)N/(14)N isotope composition (δ(15)N) of a tissue is a consequence of its N source and N physiological mechanisms in response to the environment. It could potentially be used as a tracer of N metabolism in plants under changing environmental conditions, where primary N metabolism may be complex, and losses and gains of N fluctuate over time. In order to test the utility of δ(15)N as an indicator of plant N status in N2-fixing plants grown under various environmental conditions, alfalfa (Medicago sativa L.) plants were subjected to distinct conditions of [CO2] (400 vs. 700 μmol mol(-1)), temperature (ambient vs. ambient +4°C) and water availability (fully watered vs. water deficiency-WD). As expected, increased [CO2] and temperature stimulated photosynthetic rates and plant growth, whereas these parameters were negatively affected by WD. The determination of δ(15)N in leaves, stems, roots, and nodules showed that leaves were the most representative organs of the plant response to increased [CO2] and WD. Depletion of heavier N isotopes in plants grown under higher [CO2] and WD conditions reflected decreased transpiration rates, but could also be related to a higher N demand in leaves, as suggested by the decreased leaf N and total soluble protein (TSP) contents detected at 700 μmol mol(-1) [CO2] and WD conditions. In summary, leaf δ(15)N provides relevant information integrating parameters which condition plant responsiveness (e.g., photosynthesis, TSP, N demand, and water transpiration) to environmental conditions.
authors: Faculdade de Ciências, Centro Ecologia Evolução e Alterações Ambientais, Universidade de Lisboa Lisboa, Portugal.
authors: Idoia
authors: I
authors: Ariz
authors: Faculdade de Ciências, Centro Ecologia Evolução e Alterações Ambientais, Universidade de Lisboa Lisboa, Portugal.
authors: Cristina
authors: C
authors: Cruz
authors: Faculdade de Ciências, Centro Ecologia Evolução e Alterações Ambientais, Universidade de Lisboa Lisboa, Portugal.
authors: Tomé
authors: T
authors: Neves
authors: Grupo de Fisiología del Estrés en Plantas, Departamento de Biología Ambiental, Unidad Asociada al CSIC, EEAD, Zaragoza e ICVV Logroño, Spain.
authors: Juan J
authors: JJ
authors: Irigoyen
authors: Departamento de Estadística e Investigación Operativa, Universidad Pública de Navarra Pamplona, Spain.
authors: Carmen
authors: C
authors: Garcia-Olaverri
authors: Departamento de Biología Vegetal, Facultat de Biologia, Universidad de Barcelona Barcelona, Spain.
authors: Salvador
authors: S
authors: Nogués
authors: Departamento de Ciencias del Medio Natural, Universidad Pública de Navarra Pamplona, Spain.
authors: Pedro M
authors: PM
authors: Aparicio-Tejo
authors: Plant Biology and Ecology Department, Science and Technology Faculty, University of the Basque Country Leioa, Spain ; Instituto de Agrobiotecnología (IdAB), Universidad Pública de Navarra-CSIC-Gobierno de Navarra Mutilva Baja, Spain.
authors: Iker
authors: I
authors: Aranjuelo
keywords: alfalfa; climate change; growth; physiology; δ15N