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Southern hemisphere botanical ecosystems
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RESEARCH ARTICLE
Contents Vol 56(3)

Overcoming physiological dormancy in Prostanthera eurybioides (Lamiaceae), a nationally endangered Australian shrub species

P. J. Ainsley A B D E , M. K. Jones A C and T. E. Erickson A D
+ Author Affiliations
- Author Affiliations

A Botanic Gardens of Adelaide, Seed Conservation Centre, North Terrace, Adelaide, SA 5000, Australia.

B The University of Adelaide, School of Earth and Environmental Sciences, 230 North Terrace, SA 5005, Australia.

C HortResearch, 120 Mount Albert Road, Auckland 1142, New Zealand.

D Science Division, Department of Environment and Conservation, Locked Bag 104, Bentley Delivery Centre, WA 6983, Australia.

E Corresponding author. Email: ainsley.phillip@saugov.sa.gov.au

Australian Journal of Botany 56(3) 214-219 https://doi.org/10.1071/BT07130
Submitted: 9 July 2007  Accepted: 19 November 2007   Published: 21 May 2008

Abstract

Prostanthera eurybioides (Lamiaceae) is an endangered shrub endemic to South Australia. Fruits consist of four mericarps enclosed by a persistent calyx, with each seed characterised by the presence of what we are defining as a mericarp plug. Research focussed on understanding the role of the mericarp plug in the germination process, determining seed dormancy classification and germination cues. Treatments tested included combinations of pulse dry heat (60–120°C) for up to 60 min, continuous application of gibberellic acid (100 mg L–1), smoked water (10% (v/v)) and excision of the mericarp plug. Seed imbibition experiments dispelled the presence of physical dormancy. The mericarp plug was found to be acting as a mechanical barrier preventing germination. Pulse dry heat (80°C) significantly improved germination, as did removal of the mericarp plug. Smoked water inhibited germination. Based on germination response, seeds have been classified as having non-deep physiological dormancy, with maximum germination (86%) observed following a pulse heat treatment (80°C, 10 min) and removal of the mericarp plug. Natural mechanisms for overcoming dormancy are proposed.


Acknowledgements

This research was in part funded by the SACRED Seeds Project, an international collaborative conservation effort between the Botanic Gardens of Adelaide, Australia and Royal Botanic Gardens Kew, Millennium Seed Bank Project, United Kingdom. Thanks are extended to Dr Barry Conn (Royal Botanic Gardens Sydney, Australia), Dr Wolfgang Stuppy (Royal Botanic Gardens Kew, Millennium Seed Bank) and Dr Alan Paton (Royal Botanic Gardens Kew) for comments regarding naming of the seed plug structure.


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