Solanum torreanum
Citation:
Kew Bull. 52: 706. 1997.
Type:
MOZAMBIQUE. Maputo: District Matola, Boane, 27 Apr 1969, A. Balsinhas 1466 (holotype: LISC! [LISC011338]; isotype: LMA).
Last edited by:
Sandra Knapp (May 2014)
Written by:
Maria S. Vorontsova & Sandra Knapp
Habit:
Erect to scandent herb to shrub, 0.5-1.5 m, prickly. Young stems terete, sparsely stellate-pubescent to glabrous and prickly, with porrect, sessile or variously stalked trichomes, the stalks to 0.1 mm long, the rays 4-5, 0.1-0.4 mm long, the midpoints same length as the rays or up to 1 mm long, the prickles 2-7 mm long, 0.7-4 mm wide at base, curved, sometimes reflexed or almost straight, slightly flattened, inconspicuous, yellow-orange becoming orange-brown or gray, glabrous, spaced 2-13 mm apart; bark of older stems glabrous, gray-brown.
Sympodial structure:
Sympodial units plurifoliate.
Leaves:
Leaves simple, the blades 1-6 cm long, 1-3 cm wide, ca. 2 times longer than wide, ovate to elliptic, membranous to chartaceous, drying concolorous, dark red-brown, glabrescent to sparsely stellate-pubescent on both surfaces, with porrect, sessile trichomes, the rays ca. 4, 0.25-0.5 mm long, the midpoints shorter than the rays, with 0-3 prickles on both surfaces; the primary veins 2-3 pairs, the tertiary venation sometimes visible to the naked eye; base truncate to cuneate; margins lobed, the lobes ca. 2 on each side, ca. 0.4 cm long, extending ca. 1/2 of the distance to the midvein, deltate, apically obtuse to rounded; apex acute; petiole 0.2-2.5 cm long, 1/3-1/2 of the leaf blade length, glabrous to sparsely stellate-pubescent, with 0-2 prickles.
Inflorescences:
Inflorescences apparently lateral, 2-3 cm long, not branched, with 2-8 flowers, 1-2 flowers open at any one time, glabrous to sparsely stellate-pubescent, with 0-5 prickles; peduncle ca. 2 mm long; pedicels 0.7-1.6 cm long, erect, articulated at the base, weakly stellate-pubescent to glabrous, with 0-3 prickles; pedicel scars spaced 1-4 mm apart.
Flowers:
Flowers 5-merous, apparently all perfect. Calyx 4-5 mm long, sparsely stellate-pubescent, with 0-5 prickles, the lobes 3-4 mm long, deltate, apically acute. Corolla 1.5-2.5 cm in diameter, white to mauve, stellate, lobed for ca. 2/3 of the way to the base, the lobes 8-12 mm long, 3-5.5 mm wide, ovate to deltate, spreading, densely stellate-pubescent abaxially, the trichomes porrect, sessile, the rays 5-7, 0.2-0.3 mm long, the midpoints thick, ca. same length as the rays or to 0.8 mm long. Stamens equal, with the filament tube ca. 0.5 mm long, the free portion of the filaments 0.7-1 mm long; anthers 6-8 mm long, connivent to spreading, tapering, poricidal at the tips. Ovary with minute simple trichomes; style 1.2-1.6 cm long, filiform, curved, glabrous; stigma clavate.
Fruits:
Fruit a spherical berry, 1-4 per infructescence, 0.8-1.2 cm in diameter, the pericarp smooth, evenly green when young, orange to deep red at maturity, glabrous; fruiting pedicels 1.5-1.9 cm long, ca. 0.5 mm in diameter at base, herbaceous to woody, pendulous, unarmed; fruiting calyx lobes elongating to ca. 7 mm long, ca. 1/3 the length of the mature fruit, with 0(-5) prickles.
Seeds:
Seeds ca. 10-20 per berry, 2.5-3.5 mm long, 2-3 mm wide, flattened-reniform, pale yellow-orange, the surface smooth, shiny, with raised outlines of cells or small pits.
Chromosome number:
Not known
Distribution:
Southern Mozambique and adjacent South Africa and Swaziland; growing in dry Acacia (Vachellia) woodland, thorn-bush, disturbed vegetation, on sandy or sandy-clay soils; 0-500 m elevation.
Phenology:
Flowering and fruiting March-July and October-December.
Phylogeny:
Solanum torreanum has not been included in any molecular analyses to date. It is certainly a member of the Old World Clade within subgenus Leptostemonum (Levin et al., 2006).
References:
Levin, R.A., N.R. Myers, & L. Bohs 2006. Phylogenetic relationships among the "spiny" solanums (Solanum subgenus Leptostemonum). Amer. J. Bot. 93: 157-169.
Solanum torreanum is a rare climber recognizable by its deeply lobed leaves that are dark on herbarium specimens and curved prickles. The few known collections have often been misidentified as S. capense due to the shared dark reddish color leaves on dry herbarium specimens and curved prickles, but S. torreanum is further north that any known population of S. capense and has larger leaves and more flowers per inflorescence.
Solanum torreanum is also similar to the widespread South African S. rubetorum, and can be distinguished from it by the hooked prickles (versus prickles mostly straight in S. rubetorum), and petioles 1/3-1/2 of the leaf length (versus ¼-1/3 of the leaf length in S. rubetorum). Solanum torreanum occurs within the distribution range of S. catombelense; it is easy to distinguish from the latter by its dark red-brown leaf color on herbarium specimens (versus dull gray-green, sometimes yellow-green leaf color in S. catombelense), corolla 1.5-2.5 cm in diameter (versus 0.9-1.3 cm in diameter in S. catombelense), and porrect trichomes on the stems and abaxial sides of the leaf with 4(5) rays (versus 6-8 rays in S. catombelense).