Understanding seed dormancy and germination aids conservation of rainforest species from tropical montane cloud forest: a case study confirming morphophysiological dormancy in the genus Tasmannia
Ganesha S. Liyanage
A * , Catherine A. Offord A , Darren M. Crayn B , Lydia K. Guja C , Stuart Worboys B and Karen D. Sommerville A
+ Author Affiliations
- Author Affiliations
A The Australian PlantBank, Australian Institute of Botanical Science, Royal Botanic Gardens and Domain Trust, Mount Annan, NSW 2567, Australia.
B Australian Tropical Herbarium, James Cook University Nguma-Bada Campus, McGregor Road, Smithfield, Qld 4878, Australia.
C National Seed Bank, Australian National Botanic Gardens, Parks Australia, Clunies Ross Street, Acton, ACT 2601, Australia.
Australian Journal of Botany 70(6) 399-408 https://doi.org/10.1071/BT22011
Submitted: 4 February 2022 Accepted: 3 August 2022 Published: 1 September 2022
© 2022 The Author(s) (or their employer(s)). Published by CSIRO Publishing. This is an open access article distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND)
Abstract
Context: Seed dormancy is one issue hindering implementation of conservation actions for rainforest species.
Aims: We studied dormancy and germination in Tasmannia sp. Mt Bellenden Ker and Tasmannia membranea, two tropical montane rainforest species threatened by climate change, to develop a better understanding of dormancy in the species and the genus.
Methods: Dormancy was classified for T. sp. Mt Bellenden Ker on the basis of an imbibition test, analysis of embryo to seed length (E:S) ratios and germination in response to the following four dormancy-breaking treatments: (1) scarification of the seedcoat near the micropylar end; (2) removal of the seedcoat; (3) application of 100 mg L−1 or (4) 500 mg L−1 gibberellic acid. The most effective treatment was then tested on T. membranea. The requirement for light for germination was also assessed.
Key results: Both scarified and intact seeds imbibed water. Initial E:S ratios were <0.22 for both species and increased up to 0.74 after 40 days, just before radicle emergence, for T. sp. Mt Bellenden Ker. Germination proportions were significantly higher in Treatments 1 and 2 than the remaining treatments for T. sp. Mt Bellenden Ker; T. membranea responded similarly well to Treatment 1. Germination under alternating light/dark conditions was slightly, but not significantly, greater than germination in the dark alone.
Conclusions: Both species have morphophysiological dormancy and treatments that remove seedcoat resistance to embryo growth facilitate germination. These treatments may improve germination in other species from the genus Tasmannia.
Implications: This knowledge will aid the germination of seeds to implement conservation strategies for Tasmannia spp.
Keywords: endemic species, E:S ratio, morphophysiological dormancy, plant conservation, seed dormancy, seed germination, seed storage, Tasmannia, tropical rainforests.
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