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.
Vernonia brachycalyx (Image: S. Wood, RBG Kew)
This species most probably has Orthodox seeds - dry to 15-20% eRH and store at -20ºC, or as cool as possible.
Germinate on agar, germination paper or sand at 15 or 20ºC. 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 other species in the same genus). 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.
(Image: S. Wood, RBG Kew)
Accepted name: Vernonia brachycalyx C.Hoffm.
Synonyms: Vernonia brachycalyx var. megana Cufod., Vernonia hoffmanniana S.Moore, Vernonia jodopappa Chiov., Vernonia jodopapposa Chiov. ex Lanza, Vernonia jodopapposa forma erecta Chiov. ex Lanzak, Vernonia meiocalyx S.Moore.
References and Links
- 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.
- AFPD (African Flowering Plants Database) - Conservatoire et Jardin Botaniques de la Ville de Genève, Switzerland, and South African National Biodiversity Institute, Pretoria, RSA: Vernonia brachycalyx.
- PROTAbase (Plant Resources of Tropical Africa) - Wageningen, Netherlands: Vernonia brachycalyx.
- SID (Seed Information Database) - Royal Botanic Gardens, Kew, UK: Vernonia brachycalyx.
- Tropicos - Missouri Botanical Garden, USA: Vernonia brachycalyx.