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Micropylar seed coat restraint and embryonic response to heat shock and smoke control seed dormancy in Grevillea juniperina

Published online by Cambridge University Press:  13 June 2016

Candida L. Briggs ,
E. Charles Morris  and
Glenn Stone
Candida L. Briggs
Affiliation:
School of Science and Health, University of Western Sydney, Locked Bag 1797, Penrith, NSW 2751, Australia
E. Charles Morris*
Affiliation:
School of Science and Health, University of Western Sydney, Locked Bag 1797, Penrith, NSW 2751, Australia
Glenn Stone
Affiliation:
School of Computing, Engineering and Mathematics, University of Western Sydney, Locked Bag 1797, Penrith, NSW 2751, Australia
*
*Correspondence Email: [email protected]
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Abstract

Seeds of some eastern Australian Grevillea species show the characteristics of non-deep physiological dormancy, which is broken by exposure to heat shock and/or smoke. The current study tested whether the restrictive effect of the seed coat on germination was localized to specific regions, whether the fire cues affected the growth potential of the embryo, the mechanical strength of the seed coat itself, and the anatomy of fracturing of the seed coat. Removal of the micropylar seed coat allowed germination, while retaining it in place restricted germination. The growth potential of the embryo was increased by exposure to heat shock or to smoke, and increased the most if exposed to both cues. Estimation of the minimum force required by embryos to germinate from intact seeds suggested that this force was reduced for seeds treated with fire cues. The fire cues did not affect the resistance of the seed coat to compressive force when tested after 24 h of imbibition. Fracturing of the seed coat occurred between cell walls, except for the palisade layer, where fracturing occurred across palisade and sclerenchyma cells. While the micropylar end of the seed coat imposes dormancy, most likely by mechanical constraint, heat shock and smoke overcome dormancy by increasing the embryo's growth potential and possibly weakening the seed coat, either directly or via the embryo.

Keywords

embryonic growth potentialmechanical constraintnon-deep physiological dormancyselective seed coat removalwater potential
Type
Research Papers
Information
Seed Science Research , Volume 26 , Issue 2 , June 2016 , pp. 111 - 123
Copyright
Copyright © Cambridge University Press 2016 

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