Why are the seeds of this species difficult? Some species of the Asteraceae family can produce a high proportion of empty seeds, which collectors and curators must take account of. Seeds of this species may have physiological dormancy. The seeds are relatively short-lived, so may not remain viable for a long time in storage.
Helianthus annuus (Image: W. Stuppy, RBG Kew)
This species has Orthodox seeds - dry to 15-20% eRH and store at -20ºC, or as cool as possible.
The seeds are relatively Short-lived. Monitor viability at least every five years, and more frequently once viability begins to decline. When viability falls close to the regeneration standard, the collection will need to be re-generated or re-collected.
Germinate on agar, germination paper or sand with a constant temperature of 20 or 25ºC, or under an alternating temperature regime of 30/20ºC (with 8hrs light and 16hrs darkness). Perform a cut-test on any seeds that have not germinated, to check for empty seeds. All empty seeds are non-viable in germination tests.
The seeds of this species may be Physiologically Dormant. If germination is low, this type of seed dormancy can be overcome by mimicking the seasonal patterns of the species' native habitat. Use a moist pre-chill or pre-heat treatment (depending on local climatic conditions) or a dry after-ripening treatment, before germinating the seeds on agar, germination paper or sand at their optimum temperature. If this does not work, you can perform delicate surgery to enable the embryo to grow. Excise the tissue near the root tip.
The production of empty seeds is common in non-domesticated species of the Asteraceae. Empty seeds may have a normal seed coat but an absent or under-developed embryo, or limited storage tissue.
See images of this species at the Digital Seed Atlas of the Netherlands.
Accepted name: Helianthus annuus L.
Common name: sunflower
References and Links
- Baskin, C.C. and Baskin J.M. (1998). Seeds: ecology, biogeography, and evolution of dormancy and germination. Academic Press, USA.
- Black, M., Bewley, J.D. and Halmer, P. (2006). The Encyclopaedia of Seeds: science, technology and uses. CAB International, UK.
- Food and Agriculture Organization of the United Nations and International Plant Genetic Resources Institute (1994). Genebank Standards. FAO/IPGRI, Rome, Italy.
- International Seed Testing Association (2010). International Rules for Seed Testing: edition 2010. ISTA, Bassersdorf, Switzerland.
- Rao, N.K., Hanson, J., Dulloo, M.E., Ghosh, K., Nowell, D. and Larinde, M. (2006). Manual of seed handling in genebanks. Handbooks for Genebanks No. 8. Bioversity International, Rome, Italy.
- Walters, C., Wheeler, L.M., Grotenhuis, J.M. (2005). Longevity of seeds stored in a genebank: species characteristics. Seed Science Research, Vol 15 (1): pp1-20.
- AFPD (African Flowering Plants Database) - Conservatoire et Jardin Botaniques de la Ville de Genève, Switzerland, and South African National Biodiversity Institute, Pretoria, RSA: Helianthus annuus.
- PROTAbase (Plant Resources of Tropical Africa) - Wageningen, Netherlands: Helianthus annuus.
- SID (Seed Information Database) - Royal Botanic Gardens, Kew, UK: Helianthus annuus.
- Tropicos - Missouri Botanical Garden, USA: Helianthus annuus.