Why are the seeds of this species difficult? Species of the Asteraceae family can produce a high proportion of empty seeds, which collectors and curators must take account of. The seeds may have physiological dormancy, which can be overcome by mimicking the seasonal patterns of the species' native habitat.
Tarchonanthus camphoratus (Image: S. Wood, RBG Kew)
This species most probably has Orthodox seeds (based on other species in the same family) - dry to 15-20% eRH and store at -20ºC, or as cool as possible.
Germinate on agar, germination paper or sand, under an alternating temperature regime of 25/15°C (with an 8/16hr photoperiod). 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 (based on members of the same family). If germination is low, overcome dormancy 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.
Accepted name: Tarchonanthus camphoratus L.
Synonyms: Tarchonanthus abyssinicus Sch.Bip. ex Schweinf. & Asch., Tarchonanthus camphoratus var. litakunensis (DC.) Harv., Tarchonanthus litakunensis DC., Tarchonanthus procerus Salisb.
References and Links
- Food and Agriculture Organization of the United Nations and International Plant Genetic Resources Institute (1994). Genebank Standards. FAO/IPGRI, Rome, Italy.
- Black, M., Bewley, J.D. and Halmer, P. (2006). The Encyclopaedia of Seeds: science, technology and uses. CAB International, UK.
- AFPD (African Flowering Plants Database) - Conservatoire et Jardin Botaniques de la Ville de Genève, Switzerland, and South African National Biodiversity Institute, Pretoria, RSA: Tarchonanthus camphoratus.
- PROTAbase (Plant Resources of Tropical Africa) - Wageningen, Netherlands: Tarchonanthus camphoratus.
- SID (Seed Information Database) - Royal Botanic Gardens, Kew, UK: Tarchonanthus camphoratus.
- Tropicos - Missouri Botanical Garden, USA: Tarchonanthus camphoratus.