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Titre :	Membranes an seed dormancy : beyond the anaesthetic hypothesis
Type de document :	Tiré à part de revue
Auteurs :	Barbara P. Hallett ; J. Derek Bewley
Année de publication :	2002
Importance :	69-82
Langues :	Anglais (eng)
Catégories :	[CBNPMP-Thématique] Dormance
Résumé :	The breaking of dormancy in seeds can be elicited by many factors, including temperature and short exposure to low molecular weight amphipathic molecules such as primary alcohols, monocarboxylic acids and anaesthetics. Their action has been suggested to be mediated through effecting changes to membranes. Paradoxically, though, these molecules can inhibit the germination of some non-dormant seeds. Here, we review the structure–activity relationships between amphipathic molecules and dormancy breaking and, based on the known responses of membranes to them and to temperature changes, offer an alternative interpretation of the data and a new hypothesis to explain their action. We suggest that amphipathic molecules break dormancy by partitioning into the membrane, thereby increasing and optimizing phospholipid headgroup spacing. This, in turn, facilitates the binding and activation of a peripheral membrane protein component of a signal transduction pathway that is essential for the completion of germination. In cases where amphipathic molecules inhibit germination, it is predicted that they cause the optimal headgroup spacing to be exceeded, thus preventing subsequent association of the membrane with the peripheral protein component. The hypothesis is extended to explain membrane changes that can lead to dormancy breaking during dry after-ripening.
Lien pérenne :	DOI : 10.1079/SSR200299
Permalink :	https://biblio.cbnpmp.fr/index.php?lvl=notice_display&id=131023

Membranes an seed dormancy : beyond the anaesthetic hypothesis [Tiré à part de revue] / Barbara P. Hallett ; J. Derek Bewley . - 2002 . - 69-82.
Langues : Anglais (eng)

Catégories :	[CBNPMP-Thématique] Dormance
Résumé :	The breaking of dormancy in seeds can be elicited by many factors, including temperature and short exposure to low molecular weight amphipathic molecules such as primary alcohols, monocarboxylic acids and anaesthetics. Their action has been suggested to be mediated through effecting changes to membranes. Paradoxically, though, these molecules can inhibit the germination of some non-dormant seeds. Here, we review the structure–activity relationships between amphipathic molecules and dormancy breaking and, based on the known responses of membranes to them and to temperature changes, offer an alternative interpretation of the data and a new hypothesis to explain their action. We suggest that amphipathic molecules break dormancy by partitioning into the membrane, thereby increasing and optimizing phospholipid headgroup spacing. This, in turn, facilitates the binding and activation of a peripheral membrane protein component of a signal transduction pathway that is essential for the completion of germination. In cases where amphipathic molecules inhibit germination, it is predicted that they cause the optimal headgroup spacing to be exceeded, thus preventing subsequent association of the membrane with the peripheral protein component. The hypothesis is extended to explain membrane changes that can lead to dormancy breaking during dry after-ripening.
Lien pérenne :	DOI : 10.1079/SSR200299
Permalink :	https://biblio.cbnpmp.fr/index.php?lvl=notice_display&id=131023

Titre :	Physical dormancy in Geraniaceae seeds
Type de document :	Tiré à part de revue
Auteurs :	Anke Meisert (1969-)
Année de publication :	2002
Importance :	121-128
Langues :	Anglais (eng)
Catégories :	[CBNPMP-Thématique] Dormance
Mots-clés :	Erodium manescavii Cosson  Geraniacées
Résumé :	Seed dormancy was analysed in Geraniaceae, testing 29,103 seeds of 35 species for seed-coat impermeability to water. Seeds of wild and cultivated species from a number of different climatic/ecological zones (northern Germany, the Canary Islands and South Africa) were investigated. Seeds from cultivated plants and natural populations had similar (±2%) percentages of water-impermeable seeds. The percentages of impermeable seeds at maturity were also mostly constant (±2%) for two different years. The species analysed contained from 0 to 100% impermeable seeds at maturity, and could be classified into three quantitative types of physical dormancy: four species with no impermeable seeds (PY0), 10 species with a maximum of 80% impermeable seeds (PY80), and 21 species with more than 80% impermeable seeds (PY100). Species with different life cycles and from very different habitats, e.g. Geranium pratense or Pelargonium capitatum, belonged to the PY100 group. However, all of the succulent shrubs investigated from the genus Pelargonium were PY0 species. Five years of dry storage at 20 ± 5°C decreased physical dormancy in a species-dependent fashion. Erodium cicutarium, for example, had 95% impermeable seeds at maturity; all of them became permeable during the dry storage and began to germinate immediately after placing them on a moist substrate. Physical dormancy of other species, e.g. Pelargonium zonale, Pelargonium vitifolium or Geranium pratense, was not affected by dry storage. Thus, physical dormancy is a diversely differentiated feature in Geraniaceae with regard to both percentages of impermeable seeds at maturity and maintenance of dormancy under particular conditions.
Lien pérenne :	DOI : 10.1079/SSR2002104
Permalink :	https://biblio.cbnpmp.fr/index.php?lvl=notice_display&id=131031

Physical dormancy in Geraniaceae seeds [Tiré à part de revue] / Anke Meisert (1969-) . - 2002 . - 121-128.
Langues : Anglais (eng)

Catégories :	[CBNPMP-Thématique] Dormance
Mots-clés :	Erodium manescavii Cosson  Geraniacées
Résumé :	Seed dormancy was analysed in Geraniaceae, testing 29,103 seeds of 35 species for seed-coat impermeability to water. Seeds of wild and cultivated species from a number of different climatic/ecological zones (northern Germany, the Canary Islands and South Africa) were investigated. Seeds from cultivated plants and natural populations had similar (±2%) percentages of water-impermeable seeds. The percentages of impermeable seeds at maturity were also mostly constant (±2%) for two different years. The species analysed contained from 0 to 100% impermeable seeds at maturity, and could be classified into three quantitative types of physical dormancy: four species with no impermeable seeds (PY0), 10 species with a maximum of 80% impermeable seeds (PY80), and 21 species with more than 80% impermeable seeds (PY100). Species with different life cycles and from very different habitats, e.g. Geranium pratense or Pelargonium capitatum, belonged to the PY100 group. However, all of the succulent shrubs investigated from the genus Pelargonium were PY0 species. Five years of dry storage at 20 ± 5°C decreased physical dormancy in a species-dependent fashion. Erodium cicutarium, for example, had 95% impermeable seeds at maturity; all of them became permeable during the dry storage and began to germinate immediately after placing them on a moist substrate. Physical dormancy of other species, e.g. Pelargonium zonale, Pelargonium vitifolium or Geranium pratense, was not affected by dry storage. Thus, physical dormancy is a diversely differentiated feature in Geraniaceae with regard to both percentages of impermeable seeds at maturity and maintenance of dormancy under particular conditions.
Lien pérenne :	DOI : 10.1079/SSR2002104
Permalink :	https://biblio.cbnpmp.fr/index.php?lvl=notice_display&id=131031