Seed research

Researchers at the NSW Seedbank investigate the seed biology of NSW native species, specifically targeting plant groups considered difficult to germinate or store and plants of conservation or horticultural interest.

This research aims to:

Improve the quality of seed collections held in the NSW Seedbank to ensure optimal long term storage
Determine the best methods to germinate seed by mimicking environmental cues experienced by seed in the field, including breaking dormancy in some species
Estimate how long seeds are likely to survive in storage, using rapid ageing techniques
Identify species with characteristics that suggest they may not survive the drying process, that is, desiccation sensitive or �recalcitrant� species, and investigate alternative methods of storage
Assist with threatened species management and recovery planning by providing information to other government agencies, land managers and the public.

The SeedQuest NSW research team works closely with scientists studying native seed biology in other parts of Australia, as well as with the Millennium Seed Bank team in the UK.

Seed germination and dormancy

Seeds require specific temperature, moisture and light cues to germinate, to ensure that they begin to grow when temperatures are not too harsh and rainfall is sufficient to keep the tiny seedlings alive. If moisture, appropriate temperature and light conditions are provided, but seed still does not germinate, then two things may have happened - the seed is dead or the seed is dormant.

Dormancy is a characteristic of the seed that defines the environmental conditions required for germination. It is influenced by genetics and by the environment, both during seed maturation and following seed dispersal. Dormancy ensures that seeds germinate under favourable conditions and often, over an extended period of time rather than all in one flush. This minimises the risk that all seedlings will be destroyed soon after germination and ensures species survival into the future.

Cues to break dormancy include seasonal temperature cycles, heat from fires or hot days, smoke, stratification (exposing moistened seed to a period of warm or cold), afterripening (maturation in dry conditions following dispersal) and scarification (breaks in the seed coat). Determining which cues operate in the field to break dormancy helps researchers choose which conditions will get seeds to germinate in the laboratory. In the lab, germination may also be stimulated by chemicals such as gibberellic acid. Seeds may also be scarified by chipping the coat with a scalpel or abrading with sandpaper. Storage in the seedbank may also change the germination response to particular cues.

Many Australian species have unknown dormancy and germination mechanisms. This hampers efforts to germinate seeds from conservation seed banks for the recovery of threatened species, as well as limits our ability to predict and manage populations in the field. It also means many popular Australian ornamental species are propagated by cuttings rather than from seed. Australian plant families with known dormancy include Cyperaceae, Dilleniaceae, Ericaceae (Epacridaceae), Goodeniaceae, Lamiaceae, Restionaceae, Rutaceae and Violaceae. These families are the focus of dormancy breaking studies at the NSW Seedbank, with the aim of promoting germination in the laboratory and providing information for management of common and threatened species in the field.

Seed quality and viability

The NSW Seedbank aims to make high quality seed collections of common and threatened species from throughout the state. Seed quality can be measured by several parameters, with different levels of complexity for different purposes. Our aim is to store a collection of pure viable seed, without frass (aborted seed or packing around the seed) or empty, damaged or predated seeds.

When seed collections come into the NSW Seedbank, seed fill is checked, that is, the proportion of seeds with intact endosperm and embryo. This can be determined by cutting seeds in half with a scalpel and examining under a dissecting microscope (called a �cut test�). In some species, seed fill can also be determined by floatation - filled seed will sink while empty seed will float. Seed can also be X-rayed to determine seed fill, although the success of this technique depends on the size and structure of the seed.

In addition, we need to determine whether the seed is alive (viable). This can be difficult, as intact living and dead seeds look exactly the same! The simplest test of viability is the germination test, as seeds that germinate are definitely alive. This works well if the conditions required for germination are known. However, if we don�t know the optimal test conditions for that species, or seeds are dormant, there may be a proportion of viable seeds that do not germinate. This can lead to a significant underestimate of viability. The cut test can be used to estimate seed viability, as the endosperm and embryo tissue in viable seeds is usually firm and white. The cut test is simple, quick and inexpensive. Biochemical tests such as the tetrazolium test can also be used. The tetrazolium test stains viable tissues red, while dying or dead tissues are unstained or pale pink. The tetrazolium test is more accurate but is time consuming and requires experience and skill. For example, fungal infection of seeds can also lead to red staining, as the fungal mycelium is alive too! Other biochemical stains, such as fluorescein diacetate and Evans Blue, are used to determine the viability of orchid seeds.

Seed viability varies with environmental conditions, collection season and seed maturity at collection. Some species may also have inherently low viability. After collection, viability can be further reduced by poor storage conditions and by seed ageing, even under ideal storage conditions.

Seed longevity

The recent discovery that seeds more than 200 years old could germinate and grow into healthy plants has caused great excitement at the NSW Seedbank, where seed collections are being stored as part of the international conservation partnership, SeedQuest NSW. The seeds were discovered in an archive on the other side of the world and germinated at the Millennium Seed Bank of the Royal Botanic Gardens Kew, in the UK. The seeds of 32 species were collected by Dutch explorer Jan Teerlink during a voyage to the Cape of Good Hope in 1803. The seeds were in carefully labelled envelopes and packed in a leather notebook, which had travelled on Teerlink�s ship before being stored in the Tower of London and then in the National Archives at Kew in England.

Although many seeds had not survived, three species germinated � a Leucospermum from the family Proteaceae, and two species from the family Fabaceae including an Acacia and a legume called Liparia villosa. �According to models of seed survival, even the toughest cereal seeds should have died after so long', says Matt Daws, seed scientist at the Millennium Seed Bank. �If seed can survive that long in poor conditions, then that's good news for those in the Millennium Seed Bank stored under ideal conditions.'

This is excellent news for NSW, as more than 800 seed collections from around the state have been banked as part of the SeedQuest NSW project. Many of these seed collections are from long lived species such as acacias, eucalypts, and casuarinas. The long lifespan expected for many Australian species is illustrated in NSW by a small batch of Acacia pycnantha seed originating from Australia�s first Arbor Day in 1890, where 80% of seed germinated in 1990 after 100 years of unsealed home storage.

Investigations of seed life span are a critical activity of scientists at the Australian Botanic Garden. These experiments aim to rank seed of different species from shortest to longest lived, to determine which species are likely to survive for long periods in storage and which will need to be replenished regularly with fresh seed. Scientists at the Australian Botanic Garden are collaborating with the Millennium Seed Bank, and Australian partners at Kings Park Botanic Garden in Western Australia and Botanic Gardens of Adelaide in South Australia to produce a �snapshot� of seed life span in storage. Click here to see a description of the technique used to investigate seed life span.

The discovery from the National Archives adds to well-verified stories of seed survival and germination, including 600 year old Canna seed and Nelumbo (sacred lotus) seed around 1300 years old.

Publications from Mount Annan on seed biology and ex situ conservation

Seed, L., Martyn, A.J. and Offord, C.A. (2006). Seed viability in serotinous species of the Sydney region. Australasian Plant Conservation15 (1): 8-9.
von Richter, L., Little, D. and Howell, J. (in press). Progress in research on fire-related responses of seeds in grassy woodlands in western Sydney. Proceedings of the Fifth Australian Workshop on Native Seed Biology, ACMER, Brisbane. 5 pp.
Offord, C and von Richter, L. (2005). Effect of storage temperature on germination and viability of flannel flower seed. Abstracts of the 8th International Workshop on Seeds, Germinating New Ideas. 8-13th May 2005, Brisbane, Australia.
Offord, C., Meagher, P., Cui, P., Duke, R., and Duke, C. (2005). Conservation of Wollemia nobilis seed: effects of moisture content and low temperature storage. Abstracts of the 8th International Workshop on Seeds, Germinating New Ideas. 8-13th May 2005, Brisbane, Australia.
Offord, C.A., Mckensy, M.L., Cuneo, P.V. (2004). Critical review of threatened species collections in the NSW Seedbank: Implications for ex situ conservation of biodiversity. Pacific Conservation Biology 10(4): 221-236.
Offord, C., Meagher, P., Cui, P.H., Duke, R. and Duke, C. (2004) Storage of Wollemia nobilis seed: effects of moisture content and temperature on germination, survival and fatty acid content. Abstracts of the Fifth Australian Workshop on Native Seed Biology, ACMER, Brisbane. Abst.
Offord, C., McKensy, M., Brien, J., Errington, G. and Cuneo, P. (2003). Germination and ex situ storage of Hakea dohertyi (Proteaceae) seed. Cunninghamia 8(1): 129-132.
Offord, C., Cuneo, P., McKensy, M., von Richter, L. and Johnstone, R. (2003). NSW Seedbank threatened species viability assessment. A project undertaken for the NSW Biodiversity Strategy. Draft report. 28 pp.
Martyn, A., Tyler, J., Offord, C. and McConchie, R. (2003). Swainsona sejuncta: A species of ornamental promise or a potential weed? Australian Journal of Experimental Agriculture 43 (11): 369-1381.
von Richter, L., Azzopardi, A., Johnstone, R. and Offord, C. (2001). Seed germination in the rare shrub Grevillea kennedyana (Proteaceae). Cunninghamia 7: 205-212.
Offord, C.A. and Meagher, P.F. (2001). The effects of temperature, light and stratification on seed germination of Wollemi pine (Wollemia nobilis, Araucariaceae). Australian Journal of Botany 49: 699-704.
Offord, C.A. and Tyler, J, L. 1997. Ex situ conservation of rare and endangered Australian plant species. In �Conservation into the 21st Century�. (Ed D. Touchell and K.W. Dixon) pp. 239-244, (Kings Park and Botanic Garden: Perth W.A.).
Offord, C.A. (1992). Ex situ conservation of Pultenaea parviflora. Danthonia 1: 6-7.

Other relevant web pages

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Seed-test-1

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Amelia Martyn examining a seed test

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Germination tests in cabinet

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Geijera parviflora fruits in situ

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Boronia anemonifolia grown from seed

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Squeezing Callistemon seed can help distinguish good seed from frass.

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X-ray of Carex fascicularis seed � 2 of these seeds would be considered empty and a 3rd damaged or inviable (Image supplied by W. Woodward, University of Queensland).

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X-ray of Philotheca ciliata seed � 5 of these seeds would be considered empty or inviable, including 2 predated seed where the grub is visible inside (Image supplied by W. Woodward, University of Queensland)