Seed Science Research 15: 281-307 (2005)

Plant hormone interactions during seed dormancy release and germination

Birgit Kucera, Marc Alan Cohn, Gerhard Leubner-Metzger

Institut für Biologie II (Botanik/Pflanzenphysiologie), Albert-Ludwigs-Universität Freiburg, Schänzlestr. 1, D-79104 Freiburg i. Br., Germany, Web: 'The Seed Biology Place' http://www.seedbiology.de (B.K., G.L.-M.) Department of Plant Pathology and Crop Physiology, Louisiana State University Agricultural Center, 302 Life Sciences Building, Baton Rouge, Louisiana 70803, U.S.A. (M.A.C.) Received 27 May 2005; accepted after revision 27 August 2005

Abstract.  This review focuses mainly on eudicot seeds, and on the interactions between abscisic acid (ABA), gibberellins (GA), ethylene, brassinosteroids (BR), auxin and cytokinins in regulating the interconnected molecular processes that control dormancy release and germination. Signal transduction pathways, mediated by environmental and hormonal signals, regulate gene expression in seeds. Seed dormancy release and germination of species with coat dormancy is determined by the balance of forces between the growth potential of the embryo and the constraint exerted by the covering layers, e.g. testa and endosperm. Recent progress in the field of seed biology has been greatly aided by molecular approaches utilizing mutant and transgenic seeds of Arabidopsis thaliana and the Solanaceae model systems, tomato and tobacco, which are altered in hormone biology. ABA is a positive regulator of dormancy induction and most likely also maintenance, while it is a negative regulator of germination. GA releases dormancy, promotes germination and counteracts ABA effects. Ethylene and BR promote seed germination and also counteract ABA effects. We present an integrated view of the molecular genetics, physiology and biochemistry used to unravel how hormones control seed dormancy release and germination. Table of contents: Introduction Abscisic acid (ABA) - a positive regulator of dormancy induction, a negative regulator of germination Gibberellins (GA) release dormancy, promote germination and counteract ABA-effects Ethylene promotes seed germination and counteracts ABA effects Brassinosteroids promote seed germination Cytokinins and auxins Summary and conclusions References Key words: abscisic acid, after-ripening, Arabidopsis, auxin, brassinosteroid, coat dormancy, cytokinin, endosperm-limited germination, ethylene, gibberellin, hormone mutants, Nicotiana, seed dormancy, seed germination, signal transduction pathways, transcription factors

Article in PDF format (484 KB) Abstract Figure 1 Figure 2 Table 1 © CABI Publishing http://hort.cabweb.org/

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