title: Seeds of Brassicaceae weeds have an inherent or inducible response to the germination stimulant karrikinolide.
abstract: OBJECTIVE
  Karrikinolide (KAR(1)) is a smoke-derived chemical that can trigger seeds to germinate. A potential application for KAR(1) is for synchronizing the germination of weed seeds, thereby enhancing the efficiency of weed control efforts. Yet not all species germinate readily with KAR(1), and it is not known whether seemingly non-responsive species can be induced to respond. Here a major agronomic weed family, the Brassicaceae, is used to test the hypothesis that a stimulatory response to KAR(1) may be present in physiologically dormant seeds but may not be expressed under all circumstances.
  
  
  METHODS
  Seeds of eight Brassicaceae weed species (Brassica tournefortii, Raphanus raphanistrum, Sisymbrium orientale, S. erysimoides, Rapistrum rugosum, Lepidium africanum, Heliophila pusilla and Carrichtera annua) were tested for their response to 1 µm KAR(1) when freshly collected and following simulated and natural dormancy alleviation, which included wet-dry cycling, dry after-ripening, cold and warm stratification and a 2 year seed burial trial.
  
  
  RESULTS
  Seven of the eight Brassicaceae species tested were stimulated to germinate with KAR(1) when the seeds were fresh, and the remaining species became responsive to KAR(1) following wet-dry cycling and dry after-ripening. Light influenced the germination response of seeds to KAR(1), with the majority of species germinating better in darkness. Germination with and without KAR(1) fluctuated seasonally throughout the seed burial trial.
  
  
  CONCLUSIONS
  KAR(1) responses are more complex than simply stating whether a species is responsive or non-responsive; light and temperature conditions, dormancy state and seed lot all influence the sensitivity of seeds to KAR(1), and a response to KAR(1) can be induced. Three response types for generalizing KAR(1) responses are proposed, namely inherent, inducible and undetected. Given that responses to KAR(1) were either inherent or inducible in all 15 seed lots included in this study, the Brassicaceae may be an ideal target for future application of KAR(1) in weed management.
authors.affiliation: School of Plant Biology, The University of Western Australia, 35 Stirling Highway, Crawley 6009, Western Australia, Australia. rowena.long@uwa.edu.au
authors.forename: Rowena L
authors.initials: RL
authors.lastname: Long
authors.forename: Jason C
authors.initials: JC
authors.lastname: Stevens
authors.forename: Erin M
authors.initials: EM
authors.lastname: Griffiths
authors.forename: Markus
authors.initials: M
authors.lastname: Adamek
authors.forename: Marta J
authors.initials: MJ
authors.lastname: Gorecki
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Powles
authors.forename: David J
authors.initials: DJ
authors.lastname: Merritt
mesh_terms: D001937:Brassica / Q000187:drug effects / Q000502:physiology; D019607:Brassicaceae / Q000187:drug effects* / Q000502:physiology; D003624:Darkness; D005663:Furans / Q000494:pharmacology*; D018525:Germination / Q000187:drug effects*; D029686:Lepidium / Q000187:drug effects / Q000502:physiology; D008027:Light; D057445:Plant Dormancy / Q000187:drug effects; D010937:Plant Growth Regulators / Q000494:pharmacology*; D057685:Plant Weeds / Q000254:growth & development*; D011714:Pyrans / Q000494:pharmacology*; D031224:Raphanus / Q000187:drug effects / Q000502:physiology; D012639:Seeds / Q000187:drug effects*; D013696:Temperature; D014904:Western Australia
chemical_list: D005663:Furans; D010937:Plant Growth Regulators; D011714:Pyrans; C557869:karrikinolide