title: Does nitrogen affect the interaction between a native hemiparasite and its native or introduced leguminous hosts?
abstract: Associations between plants and nitrogen (N)-fixing rhizobia intensify with decreasing N supply and come at a carbon cost to the host. However, what additional impact parasitic plants have on their leguminous hosts' carbon budget in terms of effects on host physiology and growth is unknown. Under glasshouse conditions, Ulex europaeus and Acacia paradoxa either uninfected or infected with the hemiparasite Cassytha pubescens were supplied (high nitrogen (HN)) or not (low nitrogen (LN)) with extra N. The photosynthetic performance and growth of the association were measured. Cassytha pubescens significantly reduced the maximum electron transport rates and total biomass of U. europaeus but not those of A. paradoxa, regardless of N. Infection significantly decreased the root biomass of A. paradoxa only at LN, while the significant negative effect of infection on roots of U. europaeus was less severe at LN. Infection had a significant negative impact on host nodule biomass. Ulex europaeus supported significantly greater parasite biomass (also per unit host biomass) than A. paradoxa, regardless of N. We concluded that rhizobia do not influence the effect of a native parasite on overall growth of leguminous hosts. Our results suggest that C. pubescens will have a strong impact on U. europaeus but not A. paradoxa, regardless of N in the field.
authors.affiliation: School of Biological Sciences, The University of Adelaide, Adelaide, SA, 5005, Australia.
authors.forename: Robert M
authors.initials: RM
authors.lastname: Cirocco
authors.affiliation: School of Biological Sciences, The University of Adelaide, Adelaide, SA, 5005, Australia.
authors.forename: José M
authors.initials: JM
authors.lastname: Facelli
authors.affiliation: School of Biological Sciences, The University of Adelaide, Adelaide, SA, 5005, Australia.|Manchester Metropolitan University, Manchester, M15 6BH, UK.
authors.forename: Jennifer R
authors.initials: JR
authors.lastname: Watling
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D018533:Biomass; D004579:Electron Transport / Q000187:drug effects; D007887:Fabaceae / Q000469:parasitology*; D006790:Host-Parasite Interactions / Q000187:drug effects*; D058865:Introduced Species; D008954:Models, Biological; D009584:Nitrogen / Q000494:pharmacology*; D010271:Parasites / Q000502:physiology*; D010788:Photosynthesis / Q000187:drug effects; D018515:Plant Leaves / Q000187:drug effects / Q000502:physiology; D055170:Plant Root Nodulation / Q000187:drug effects; D018520:Plant Shoots / Q000187:drug effects / Q000502:physiology; D013045:Species Specificity
chemical_list: D009584:Nitrogen
keywords: 
  Ulex europaeus
  ; biomass; hemiparasite; legume; nitrogen; nodulation; photosynthesis; rhizobia