Plant and Cell Physiology Advance Access published online on October 30, 2008
Plant and Cell Physiology, doi:10.1093/pcp/pcn164
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Involvement of ABA in induction of secondary dormancy in barley (Hordeum vulgare L.) seeds
1 UPMC Univ Paris 06, EA2388, Physiologie des semences, Boîte courrier 152, 4 place Jussieu, F-75005 Paris, France
2 IFEVA-Catedra de Cerealicultura Facultad de Agronomia, Universidad de Buenos Aires/CONICET, Av. San Martin 4453, 1417 Buenos Aires, Argentina
*Corresponding author: Dr. Juliette Leymarie, UPMC Univ Paris 06, EA2388, Physiologie des semences, Boîte courrier 152, 4 place Jussieu, F-75005 Paris, France, E Mail: juliette.leymarie{at}upmc.fr
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Abstract |
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At harvest, barley seeds are dormant because their germination is difficult above 20°C. Incubation of primary dormant seeds at 30°C, a temperature at which they do not germinate, results in a loss of their ability to germinate at 20°C. This phenomenon which corresponds to an induction of a secondary dormancy is already observed after a pre-treatment at 30°C as short as 4-6 h, and is optimal after 24-48 h. It is associated with maintenance of high level of embryo ABA content during seed incubation at 30°C, and after seed transfer at 20°C, while ABA content decreases rapidly in embryos of primary dormant seeds placed directly at 20°C. Induction of secondary dormancy results also in an increase in embryo responsiveness to ABA at 20°C. Application of ABA during seed treatment at 30°C has no significant additive effect on the further germination at 20°C. In contrast, incubation of primary dormant seeds at 20°C for 48 and 72 h in the presence of ABA inhibits further germination on water similarly as 24-48-h incubation at 30°C does. However fluridone, an inhibitor of ABA synthesis, applied during incubation of the grains at 30°C has only a slight effect on ABA content and secondary dormancy. Expression of genes involved in ABA metabolism (HvABA8’OH-1, HvNCED1 and HvNCED2) was studied in relation with the expression of primary and secondary dormancies. The results presented suggest a specific role for HvNCED1 and HvNCED2 in regulation of ABA synthesis in secondary seed dormancy.
Keywords: ABA 8'hydroxylase - Abscisic acid - Barley grain - Hordeum vulgare - 9-cis-epoxycarotenoid dioxygenase - secondary seed dormancy
(Received October 9, 2008; Accepted October 27, 2008)
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