title: Patterns of Growth Costs and Nitrogen Acquisition in Cytisus striatus (Hill) Rothm. and Cytisus balansae (Boiss.) Ball are Mediated by Sources of Inorganic N.
abstract: Nitrogen-fixing shrubby legumes in the Mediterranean area partly overcome nutrient limitations by making use of soil N and atmospheric N₂ sources. Their ability to switch between different sources lets them adjust to the carbon costs pertaining to N acquisition throughout the year. We investigated the utilization of different inorganic N sources by Cytisus balansae and Cytisus striatus, shrubby legumes under low and a sufficient (5 and 500 µM P, respectively) levels of P. Plants grew in sterile sand, supplied with N-free nutrient solution and inoculated with effective Bradyrhizobium strains; other treatments consisted of plants treated with (i) 500 µM NH₄NO₃; and (ii) 500 µM NH₄NO₃ and inoculation with effective rhizobial strains. The application of NH₄NO₃ always resulted in greater dry biomass production. Carbon construction costs were higher in plants that were supplied with mineral and symbiotic N sources and always greater in the endemic C. striatus. Photosynthetic rates were similar in plants treated with different sources of N although differences were observed between the two species. Non-fertilized inoculated plants showed a neat dependence on N₂ fixation and had more effective root nodules. Results accounted for the distribution of the two species with regards to their ability to use different N sources.
authors.affiliation: Department of Physical, Chemical and Natural Systems, University Pablo de Olavide, Carretera de Utrera Km, Seville 141013, Spain. maperfer@upo.es.
authors.forename: María
authors.initials: M
authors.lastname: Pérez-Fernández
authors.affiliation: Department of Physical, Chemical and Natural Systems, University Pablo de Olavide, Carretera de Utrera Km, Seville 141013, Spain. ecmagro79@gmail.com.
authors.forename: Elena
authors.initials: E
authors.lastname: Calvo-Magro
authors.affiliation: Department of Physical, Chemical and Natural Systems, University Pablo de Olavide, Carretera de Utrera Km, Seville 141013, Spain. iramroj@alu.upo.es.
authors.forename: Irene
authors.initials: I
authors.lastname: Ramírez-Rojas
authors.affiliation: Department of Physical, Chemical and Natural Systems, University Pablo de Olavide, Carretera de Utrera Km, Seville 141013, Spain. lmorgal@alu.upo.es.
authors.forename: Laura
authors.initials: L
authors.lastname: Moreno-Gallardo
authors.affiliation: Botany and Zoology Department, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa. alexvalentine@mac.com.
authors.forename: Valentine
authors.initials: V
authors.lastname: Alexander
keywords: C construction costs; N2 fixation; legume; mineral N