title: The morphophysiological dormancy in Amborella trichopoda seeds is a pleisiomorphic trait in angiosperms.
abstract: Recent parsimony-based reconstructions suggest that seeds of early angiosperms had either morphophysiological or physiological dormancy, with the former considered as more probable. The aim of this study was to determine the class of seed dormancy present in Amborella trichopoda , the sole living representative of the most basal angiosperm lineage Amborellales, with a view to resolving fully the class of dormancy present at the base of the angiosperm clade.
  
  
  
  Drupes of A. trichopoda without fleshy parts were germinated and dissected to observe their structure and embryo growth. Pre-treatments including acid scarification, gibberellin treatment and seed excision were tested to determine their influence on dormancy breakage and germination. Character-state mapping by maximum parsimony, incorporating data from the present work and published sources, was then used to determine the likely class of dormancy present in early angiosperms.
  
  
  
  Germination in A. trichopoda requires a warm stratification period of at least approx. 90 d, which is followed by endosperm swelling, causing the water-permeable pericarp-mesocarp envelope to split open. The embryo then grows rapidly within the seed, to radicle emergence some 17 d later and cotyledon emergence after an additional 24 d. Gibberellin treatment, acid scarification and excision of seeds from the surrounding drupe tissues all promoted germination by shortening the initial phase of dormancy, prior to embryo growth.
  
  
  
  Seeds of A. trichopoda have non-deep simple morphophysiological dormancy, in which mechanical resistance of the pericarp-mesocarp envelope plays a key role in the initial physiological phase. Maximum parsimony analyses, including data obtained in the present work, indicate that morphophysiological dormancy is likely to be a pleisiomorphic trait in flowering plants. The significance of this conclusion for studies of early angiosperm evolution is discussed.
authors.affiliation: Institut Agronomique néo-Calédonien (IAC), BP 73 Port Laguerre, 98890 Païta, New Caledonia.|Laboratoire Insulaire du Vivant et de l'Environnement (LIVE)-EA 4243, University of New Caledonia (UNC), BP R4, 98851 Noumea, New Caledonia.
authors.forename: Bruno
authors.initials: B
authors.lastname: Fogliani
authors.affiliation: Institut Agronomique néo-Calédonien (IAC), BP 73 Port Laguerre, 98890?Païta, New Caledonia.
authors.forename: Gildas
authors.initials: G
authors.lastname: Gâteblé
authors.affiliation: Laboratoire Insulaire du Vivant et de l'Environnement (LIVE)-EA 4243, University of New Caledonia (UNC), BP R4, 98851 Noumea, New Caledonia.
authors.forename: Matthieu
authors.initials: M
authors.lastname: Villegente
authors.affiliation: Institut Agronomique néo-Calédonien (IAC), BP 73 Port Laguerre, 98890?Païta, New Caledonia.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Fabre
authors.affiliation: Institut Agronomique néo-Calédonien (IAC), BP 73 Port Laguerre, 98890 Païta, New Caledonia.|Laboratoire Insulaire du Vivant et de l'Environnement (LIVE)-EA 4243, University of New Caledonia (UNC), BP R4, 98851 Noumea, New Caledonia.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Klein
authors.affiliation: Institut Agronomique néo-Calédonien (IAC), BP 73 Port Laguerre, 98890?Païta, New Caledonia.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Anger
authors.affiliation: Department of Biology, University of Kentucky, Lexington, KY 40506, USA.|Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY 40546, USA.
authors.forename: Carol C
authors.initials: CC
authors.lastname: Baskin
authors.affiliation: Reproduction et Développement des Plantes (RDP; UMR5667, CNRS-INRA-Université de Lyon), Ecole Normale Supérieure de Lyon, 46 allée d'Italie, 69364 Lyon Cedex 07, France.
authors.forename: Charlie P
authors.initials: CP
authors.lastname: Scutt
mesh_terms: D005075:Biological Evolution; D018525:Germination / Q000502:physiology; D019684:Magnoliopsida / Q000033:anatomy & histology / Q000502:physiology* / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D057445:Plant Dormancy / Q000502:physiology*; D012639:Seeds / Q000033:anatomy & histology / Q000502:physiology* / Q000648:ultrastructure
keywords: ANA-grade angiosperm; Amborella trichopoda; Amborellaceae; evolution of seed dormancy; morphophysiological dormancy; rudimentary embryo; seed germination