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AOBPreview originally published online on September 12, 2005
Annals of Botany 2005 96(6):965-980; doi:10.1093/aob/mci250
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© The Author 2005. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org

Investigations into Seed Dormancy in Grevillea linearifolia, G. buxifolia and G. sericea: Anatomy and Histochemistry of the Seed Coat

C. L. BRIGGS1, E. C. MORRIS1,* and A. E. ASHFORD2

1 Ecology Research Group, University of Western Sydney, Locked Bag 1797, Penrith South DC, NSW 1797, Australia and 2 School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia

* For correspondence. E-mail c.morris{at}uws.edu.au

Received: 29 March 2005    Returned for revision: 23 May 2005    Accepted: 5 July 2005    Published electronically: 12 September 2005

• Background and Aims Seeds of east Australian Grevillea species generally recruit post-fire; previous work showed that the seed coat was the controller of dormancy in Grevillea linearifolia. Former studies on seed development in Grevillea have concentrated on embryology, with little information that would allow testing of hypotheses about the breaking of dormancy by fire-related cues. Our aim was to investigate structural and chemical characteristics of the seed coat that may be related to dormancy for three Grevillea species.

• Methods Seeds of Grevillea linearifolia, Grevillea buxifolia and Grevillea sericea were investigated using gross dissection, thin sectioning and histochemical staining. Water movement across the seed coat was tested for by determining the water content of embryos from imbibed and dry seeds of G. sericea. Penetration of intact seeds by Lucifer Yellow was used to test for internal barriers to diffusion of high-molecular-weight compounds.

• Key Results Two integuments were present in the seed coat: an outer testa, with exo-, meso- and endotestal (palisade) layers, and an inner tegmen of unlignified sclerenchyma. A hypostase at the chalazal end was a region of structural difference in the seed coat, and differed slightly among the three species. An internal cuticle was found on each side of the sclerenchyma layer. The embryos of imbibed seeds had a water content six times that of dry seeds. Barriers to diffusion of Lucifer Yellow existed at the exotestal and the endotestal/hypostase layers.

• Conclusions Several potential mechanisms of seed coat dormancy were identified. The embryo appeared to be completely surrounded by outer and inner barriers to diffusion of high-molecular-weight compounds. Phenolic compounds present in the exotesta could interfere with gas exchange. The sclerenchyma layer, together with strengthening in the endotestal and exotestal cells, could act as a mechanical constraint.

Key words: Seed coat structure, Grevillea linearifolia, Grevillea buxifolia, Grevillea sericea, histochemistry, seed dormancy


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C. L. Briggs and E. C. Morris
Seed-coat Dormancy in Grevillea linearifolia: Little Change in Permeability to an Apoplastic Tracer after Treatment with Smoke and Heat
Ann. Bot., April 1, 2008; 101(5): 623 - 632.
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