title: Allocating nitrogen away from a herbivore: a novel compensatory response to root herbivory.
abstract: Centaurea maculosa, an invasive North American plant species, shows a high degree of tolerance to the root-boring biocontrol herbivore, Agapeta zoegana. For example, infested individuals of C. maculosa often exhibit more rigorous growth and reproduction compared with their non-infested counterparts. Compensatory responses to aboveground herbivores often involve increases in leaf area and/or photosynthetic capacity, but considerably less is known about root system compensatory responses to belowground herbivory. We used a (15)N labeling approach to evaluate whether compensatory adjustments in N acquisition via changes in root morphology and/or physiological uptake capacity could explain the ability of C. maculosa to tolerate root herbivory. Root herbivory reduced whole plant N uptake by more than 30% and root uptake capacity by about 50%. Despite a marked reduction in N procurement, herbivory did not affect total biomass or shoot N status. Infested plants maintained shoot N status by shifting more of the acquired N from the root to the shoot. To our knowledge, shifting N allocation away from a root herbivore has not been reported and provides a plausible mechanism for the host plant to overcome an otherwise devastating effect of a root herbivore-induced N deficit.
authors.affiliation: Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA. newingha@unlv.nevada.edu
authors.forename: Beth A
authors.initials: BA
authors.lastname: Newingham
authors.forename: Ragan M
authors.initials: RM
authors.lastname: Callaway
authors.forename: Hormoz
authors.initials: H
authors.lastname: Bassirirad
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D019659:Asteraceae / Q000254:growth & development / Q000378:metabolism*; D009036:Moths / Q000502:physiology*; D009584:Nitrogen / Q000378:metabolism*; D010572:Pest Control, Biological; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism*; D012987:Soil / Q000032:analysis
chemical_list: D012987:Soil; D009584:Nitrogen