title: Wait or escape? Contrasting submergence tolerance strategies of Rorippa amphibia, Rorippa sylvestris and their hybrid.
abstract: OBJECTIVE
  Differential responses of closely related species to submergence can provide insight into the evolution and mechanisms of submergence tolerance. Several traits of two wetland species from habitats with contrasting flooding regimes, Rorippa amphibia and Rorippa sylvestris, as well as F(1) hybrid Rorippa × anceps were analysed to unravel mechanisms underlying submergence tolerance.
  
  
  METHODS
  In the first submergence experiment (lasting 20 d) we analysed biomass, stem elongation and carbohydrate content. In the second submergence experiment (lasting 3 months) we analysed survival and the effect of re-establishment of air contact on biomass and carbohydrate content. In a separate experiment we analysed expression of two carbohydrate catabolism genes, ADH1 and SUS1, upon re-establishment of air contact following submergence.
  
  
  RESULTS
  All plants had low mortality even after 3 months of submergence. Rorippa sylvestris was characterized by 100 % survival and higher carbohydrate levels coupled with lower ADH1 gene expression as well as reduced growth compared with R. amphibia. Rorippa amphibia and the hybrid elongated their stems but this did not pay-off in higher survival when plants remained submerged. Only R. amphibia and the hybrid benefited in terms of increased biomass and carbohydrate accumulation upon re-establishing air contact.
  
  
  CONCLUSIONS
  Results demonstrate contrasting 'escape' and 'quiescence' strategies between Rorippa species. Being a close relative of arabidopsis, Rorippa is an excellent model for future studies on the molecular mechanism(s) controlling these strategies.
authors.affiliation: Experimental Plant Systematics, Institute for Biodiversity and Ecosystem Dynamics, Universiteit van Amsterdam, Science Park 904, Amsterdam, The Netherlands. m.akman@uva.nl
authors.forename: Melis
authors.initials: M
authors.lastname: Akman
authors.forename: Amit V
authors.initials: AV
authors.lastname: Bhikharie
authors.forename: Elizabeth H
authors.initials: EH
authors.lastname: McLean
authors.forename: Alex
authors.initials: A
authors.lastname: Boonman
authors.forename: Eric J W
authors.initials: EJ
authors.lastname: Visser
authors.forename: M Eric
authors.initials: ME
authors.lastname: Schranz
authors.forename: Peter H
authors.initials: PH
authors.lastname: van Tienderen
mesh_terms: D000222:Adaptation, Physiological; D001483:Base Sequence; D018533:Biomass; D017931:DNA Primers; D018506:Gene Expression Regulation, Plant; D016133:Polymerase Chain Reaction; D031225:Rorippa / Q000235:genetics / Q000502:physiology*
chemical_list: D017931:DNA Primers