title: Physical dormancy in seeds: a game of hide and seek?
abstract: Historically, 'physical dormancy', or 'hard seededness', where seeds are prevented from germinating by a water-impermeable seed coat, is viewed as a dormancy mechanism. However, upon water uptake, resumption of metabolism leads to the unavoidable release of volatile by-products, olfactory cues that are perceived by seed predators. Here, we examine the hypothesis that hard seeds are an anti-predator trait that evolved in response to powerful selection by small mammal seed predators. Seeds of two legume species with dimorphic seeds ('hard' and 'soft'), Robinia pseudoacacia and Vicia sativa, were offered to desert hamsters (Phodopus roborovskii) in a series of seed removal studies examining the differences in seed harvest between hard and soft seeds. Volatile compounds emitted by dry and imbibed soft seeds were identified by headspace gas chromatography-mass spectrometry (GC-MS). Fourteen main volatile compounds were identified, and hamsters readily detected both buried imbibed seeds and an artificial 'volatile cocktail' that mimicked the scent of imbibed seeds, but could not detect buried hard or dry soft seeds. We argue that physical dormancy has evolved to hide seeds from mammalian predators. This hypothesis also helps to explain some otherwise puzzling features of hard seeds and has implications for seed dispersal.
authors: Department of Biology, University of Bergen, Postboks 7803, 5020, Bergen, Norway.|Department of Molecular Biology, University of Bergen, Postboks 7803, 5020, Bergen, Norway.
authors: Torbjørn Rage
authors: TR
authors: Paulsen
authors: Seed Conservation Department, Royal Botanic Gardens Kew, Wakehurst Place, Ardingly, West Sussex, RH17 6TN, UK.
authors: Louise
authors: L
authors: Colville
authors: Seed Conservation Department, Royal Botanic Gardens Kew, Wakehurst Place, Ardingly, West Sussex, RH17 6TN, UK.|Institute of Botany, University of Innsbruck, Sternwartestraße 15, A-6020, Innsbruck, Austria.
authors: Ilse
authors: I
authors: Kranner
authors: Seed Conservation Department, Royal Botanic Gardens Kew, Wakehurst Place, Ardingly, West Sussex, RH17 6TN, UK.|Alcoa of Australia Limited, PO Box 172, Pinjarra, WA, 6208, Australia.
authors: Matthew I
authors: MI
authors: Daws
authors: Department of Biology, University of Bergen, Postboks 7803, 5020, Bergen, Norway.
authors: Göran
authors: G
authors: Högstedt
authors: Department of Biology, University of Bergen, Postboks 7803, 5020, Bergen, Norway.
authors: Vigdis
authors: V
authors: Vandvik
authors: Department of Animal and Plant Sciences, University of Sheffield, Sheffield, S10 2TN, UK.
authors: Ken
authors: K
authors: Thompson
mesh_terms: D000818:Animals; D006224:Cricetinae; D057445:Plant Dormancy / Q000502:physiology*; D012639:Seeds / Q000502:physiology*; D012903:Smell / Q000502:physiology; D055549:Volatile Organic Compounds / Q000378:metabolism
chemical_list: D055549:Volatile Organic Compounds