Why are the seeds of this species difficult? Some species of the Poaceae family can produce a high proportion of empty seeds, which collectors and curators must take account of. The seeds may have physiological dormancy.
Digitaria exilis (Image: S. Wood, RBG Kew)
This species 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 25ºC. 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, 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.
(Image: S. Wood, RBG Kew)
The occurrence of empty seeds is common in wild-collected accessions of some Poaceae species. Empty seeds may have a normal seed coat but an absent or under-developed embryo, or limited storage tissue.
Accepted name: Digitaria exilis (Kippist) Stapf.
Synonyms: Paspalum exile Kippist
Common name: crabgrass, fingergrass
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: Digitaria exilis.
- PROTAbase (Plant Resources of Tropical Africa) - Wageningen, Netherlands: Digitaria exilis.
- SID (Seed Information Database) - Royal Botanic Gardens, Kew, UK: Digitaria exilis.
- Tropicos - Missouri Botanical Garden, USA: Digitaria exilis.