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Combinational dormancy in winter annual Fabaceae

Published online by Cambridge University Press:  30 July 2010

Jozef A. Van Assche*
Affiliation:
Laboratory of Plant Ecology, Catholic University Leuven, Kasteelpark Arenberg 31, B-3001 Leuven, Belgium
Filip E.A. Vandelook
Affiliation:
Laboratory of Plant Ecology, Catholic University Leuven, Kasteelpark Arenberg 31, B-3001 Leuven, Belgium
*
*Correspondence Fax: +3216321968 Email: jozef.vanassche@bio.kuleuven.be

Abstract

Among 14 species of herbaceous Fabaceae, all six winter annuals show a marked non-deep physiological dormancy of the embryo in addition to physical dormancy. This physiological dormancy is apparent at 23°C, but not at lower temperatures of 10°C and 5°C and disappears after 3 months of dry storage. These results corroborate the hypothesis that combinational dormancy is a double safety mechanism for delaying germination during summer: physical dormancy postpones germination, and even in early softened seeds germination is prevented by physiological dormancy of the embryo. Softened, swollen seeds of Medicago arabica tolerate a subsequent desiccation and remain viable even after five cycles of dehydration and rehydration. The rate of natural softening of M. arabica seeds increases exponentially at higher temperatures, with a Q10 between 3.4 and 5.1, and obeys the Arrhenius equation. This indicates that a chemical reaction might be involved in breakdown of physical dormancy. Winter annuals with hard seeds show similar properties as winter annuals with permeable seeds: the need for afterripening and requirement of lower temperatures delay germination until autumn. Only one species, Vicia sativa, loses physical dormancy during dry storage. Drying during summer might be a supplementary cue for germination in autumn.

Information

Type
Research Article
Copyright
Copyright © Cambridge University Press 2010

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