Dioscorea praehensilis Benth.

IUCN Red List of Threatened Species https://www.iucnredlist.org/species/20745654/20755941

Conservation

LC - least concern

J. R. Timberlake, E. S. Martins (2009). Flora Zambesiaca, Vol 12 (part 2). Royal Botanic Gardens, Kew

Type

Type Sierra Leone, ♂ fl. vi.1841, Vogel 21 (K lectotype, chosen by Wilkin 2001).

Morphology General Habit

Herbaceous twining vine to at least 10 m, less when climbing on low vegetation, usually dying back annually

Vegetative Multiplication Tubers

Tuber 1, often present alongside withered tuber of previous season, up to 5 cm diameter, at least 60 cm long, cylindric, descending vertically into substrate, white when young but periderm later turning brown

Morphology General Indumentum

Indumentum absent

Morphology Stem

Stems right-twining, concolorous to pale brown prickles concentrated on larger, cataphyll-bearing stem, most dense and largest near stem base

Morphology Leaves

Leaves opposite, rarely alternate; blade entire, apex acuminate to long-acuminate, somewhat thickened (especially distal 3–4 mm), usually longitudinally folded along midrib in herbarium specimens, cataphylls present on basal stem, usually to c.2 cm long, ovate, acuminate, thick and coriaceous with a thinner translucent margin, base often clasping node and axillary branch; lateral nodal flanges absent

Morphology Reproductive morphology Inflorescences

Inflorescence spicate, simple

sex Male

Male flowers patent to axis and 1–2(4) mm apart; outer tepals 1.4–2.1 0.8–1.6 mm, elliptic to elliptic-oblong or ovate, sometimes broadly so, thinly papery, rigid and somewhat translucent when dry, basal / often thicker but more translucent, especially in older flowers where base may appear grey in herbarium specimens; inner tepals 1.1–1.9 0.6–1.4 mm, elliptic or ovate to broadly so, occasionally obovate, erect and concave, thickly papery and opaque, stamens (5)6(9)

Morphology Reproductive morphology Fruits

Capsule not ascending at dehiscence but pendent to patent to infructescence axis, 1.5–2.4 2.8–4.3 cm, each lobe with a c.1 mm wide, semicircular opercular strip along margin which reflexes at dehiscence, pedicel swollen and obconic in mature capsule; seed wing extending all around seed margin.

Distribution

Zambia, Zimbabwe, Mozambique, Malawi. Widespread in W, C and E Africa.

Ecology

In a broad range of forest and grassland ecologys, including cultivated areas; 400–1700 m.

Phenology

Flowering in January and February; fruiting from March onwards.

Conservation

Conservation notes Widespread species; not threatened, although local varieties or races may be at risk.

Vernacular

Sometimes termed bush yam, forest yam or white yam in English.

Extinction risk predictions for the world's flowering plants to support their conservation (2024). Bachman, S.P., Brown, M.J.M., Leão, T.C.C., Lughadha, E.N., Walker, B.E. https://nph.onlinelibrary.wiley.com/doi/full/10.1111/nph.19592

Conservation

Predicted extinction risk: not threatened. Confidence: confident

Dioscoreaceae, J. Miège. Flora of West Tropical Africa 3:1. 1968

Morphology General Habit

Spiny climber 15-25 ft. high

Vegetative Multiplication Tubers

Tubers protected by spiny roots.

Dioscoreaceae, E. Milne-Redhead. Flora of Tropical East Africa. 1975

Morphology General Habit

Tuber replaced annually, up to 5 cm. in diameter and more than 6 dm. long, descending vertically, protected by horizontal thorny roots above.

Morphology Stem

Twining stems very prickly below, less so above, the lower 3 m. leafless but with thick fleshy stipules, up to 12 m. long, glabrous.

Morphology Leaves

Leaves opposite or occasionally alternate, glabrous; petiole up to 5(–7) cm. long; blade ovate, ovate-lanceolate or rarely deltoid, widely cordate or subtruncate at the base, acutely acuminate, up to 10(–15) cm. long and 5(–7.5) cm. broad.

Vegetative Multiplication Tubers

Aerial tubers absent.

Morphology Reproductive morphology Inflorescences

Inflorescences glabrous.

Morphology Reproductive morphology Flowers

Male spicate, ascending, up to 5(–7) cm. long, with the flowers not densely arranged, arising up to 5(–7) in the axils of leaves or at leafless nodes on terminal or lateral branches up to 10(–17) cm. long; perianth longer than wide with the lower half somewhat scarious, greyish or straw-coloured and the upper half petaloid, ± 2 mm. long and 1.5 mm. in diameter apically, narrower below. Female pendulous, 1 per leaf-axil, up to 15(–17) cm. long; perianth subglobose, somewhat flattened, scarcely 2 mm. across.

sex Male

Male spicate, ascending, up to 5(–7) cm. long, with the flowers not densely arranged, arising up to 5(–7) in the axils of leaves or at leafless nodes on terminal or lateral branches up to 10(–17) cm. long; perianth longer than wide with the lower half somewhat scarious, greyish or straw-coloured and the upper half petaloid, ± 2 mm. long and 1.5 mm. in diameter apically, narrower below.

sex Female

Female pendulous, 1 per leaf-axil, up to 15(–17) cm. long; perianth subglobose, somewhat flattened, scarcely 2 mm. across.

Morphology Reproductive morphology Fruits

Capsule as fig. 1/4, p. 4, up to 3.8 cm. in diameter, glaucous.

Morphology Reproductive morphology Seeds

Seeds (fig. 1/4a) winged all round.

Habitat

Rain-forest and riverine forest, termite-hills and woodland river-banks; 800–1800 m.

Distribution

widely spread to Sierra Leone in the west and Malawi, Zambia and Angola in the south K5 T4 T7 T8 U2 U3 U4