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JXB Advance Access originally published online on January 21, 2008
Journal of Experimental Botany 2008 59(2):335-347; doi:10.1093/jxb/erm315
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© 2008 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. This paper is available online free of all access charges (see http://jxb.oxfordjournals.org/open_access.html for further details)

RESEARCH PAPER

Quantifying the sensitivity of barley seed germination to oxygen, abscisic acid, and gibberellin using a population-based threshold model

Kent J. Bradford1,*, Roberto L. Benech-Arnold2, Daniel Côme3 and Françoise Corbineau3

1Department of Plant Sciences, One Shields Avenue, University of California, Davis, CA 95616-8780, USA
2IFEVA-Cátedra de Cerealicultura Facultad de Agronomia, Universidad de Buenos Aires/CONICET, Av. San Martin 4453, 1417 Buenos Aires, Argentina
3Université Pierre et Marie Curie-Paris 6, Physiologie Végétale Appliquée, EA 2388 Physiologie des semences, Site d'Ivry, Boîte 152, 4 Place Jussieu, F-75252 Paris cedex 05, France

* To whom correspondence should be addressed. E-mail: kjbradford{at}ucdavis.edu

Barley (Hordeum vulgare L.) seeds (grains) exhibit dormancy at maturity that is largely due to the presence of the glumellae (hulls) that reduce the availability of oxygen (O2) to the embryo. In addition, abscisic acid (ABA) and gibberellins (GAS) interact with O2 to regulate barley seed dormancy. A population-based threshold model was applied to quantify the sensitivities of seeds and excised embryos to O2, ABA, and GA, and to their interactive effects. The median O2 requirement for germination of dormant intact barley seeds was 400-fold greater than for excised embryos, indicating that the tissues enclosing the embryo markedly limit O2 penetration. However, embryo O2 thresholds decreased by another order of magnitude following after-ripening. Thus, increases in both permeability of the hull to O2 and embryo sensitivity to O2 contribute to the improvement in germination capacity during after-ripening. Both ABA and GA had relatively small effects on the sensitivity of germination to O2, but ABA and GA thresholds varied over several orders of magnitude in response to O2 availability, with sensitivity to ABA increasing and sensitivity to GA decreasing with hypoxia. Simple additive models of O2–ABA and O2–GA interactions required consideration of these O2 effects on hormone sensitivity to account for actual germination patterns. These quantitative and interactive relationships among O2, ABA, and GA sensitivities provide insight into how dormancy and germination are regulated by a combination of physical (O2 diffusion through the hull) and physiological (ABA and GA sensitivities) factors.

Key words: Abscisic acid, barley, germination, gibberellin, Hordeum vulgare L., model, oxygen, sensitivity

Received 2 August 2007; Revised 14 November 2007 Accepted 19 November 2007


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