title: Seed dormancy and germination of the European Chaerophyllum temulum (Apiaceae), a member of a trans-Atlantic genus.
abstract: OBJECTIVE
  The European Chaerophyllum temulum and two North American Chaerophyllum species have a trans-Atlantic disjunct distribution. This work aimed to resolve requirements for dormancy break and germination of C. temulum seeds and to compare dormancy traits with those of the two North American congeners.
  
  
  METHODS
  Phenology of germination and embryo growth was studied by regularly exhuming seeds sown in natural conditions. Temperature requirements for embryo growth, breaking of dormancy and germination were determined by incubating seeds under controlled laboratory conditions. Additionally the effect of GA(3) on germination was tested to determine the specific dormancy type.
  
  
  RESULTS
  In natural conditions, embryo growth starts in early winter. Seedlings emerge in late winter shortly after the embryos reached the critical ratio for embryo length to seed length (E : S) of approx. 0.95. Growth of the embryo only occurs during a prolonged incubation period at 5 degrees C. After stratification at 5 degrees C, which breaks physiological and morphological dormancy, seeds can germinate at a wide range of temperatures. GA(3) did not substitute for cold stratification in seeds placed at 23 degrees C.
  
  
  CONCLUSIONS
  Chaerophyllum temulum has deep complex morphophysiological dormancy. This dormancy type differs considerably from that of the two North American congeners.
authors.affiliation: Laboratory of Plant Ecology, K.U. Leuven, Kasteelpark Arenberg 31, B-3001 Leuven, Belgium. filip.vandelook@bio.kuleuven.be
authors.forename: Filip
authors.initials: F
authors.lastname: Vandelook
authors.forename: Nele
authors.initials: N
authors.lastname: Bolle
authors.forename: Jozef A
authors.initials: JA
authors.lastname: Van Assche
mesh_terms: D019661:Apiaceae / Q000254:growth & development / Q000502:physiology*; D001267:Atlantic Ocean; D005075:Biological Evolution; D018525:Germination / Q000502:physiology*; D005875:Gibberellins / Q000502:physiology*; D008027:Light; D012639:Seeds / Q000254:growth & development / Q000502:physiology*; D013045:Species Specificity; D013696:Temperature; D013997:Time Factors
chemical_list: D005875:Gibberellins; C007842:gibberellic acid