Solanum rubiginosum [Vahl ]

Solanum rubiginosum

Citation author:

Vahl

Citation:

Eclog. Amer. 2: 17. 1798.

Type:

French Guiana. “Cayenne”, J. Von Rohr s.n. (holotype, C [C-22914]; isotypes, BM [BM000887956], C, G-DC [F neg. 6823], LINN [Smith 365.9]).

Last edited by:

Knapp, S.

Written by:

A.R. Bean

Habit:

Liana 3-5 m (10), or shrub when young, woody, armed; stems erect, terete, sparsely prickly, the prickles 2-3 mm long, recurved at the apex, compressed, rusty brown, the scar oblong, pubescence tomentose to scabrous, the trichomes porrect stellate, sessile, with 6-7 rays, the midpoint reduced; new growth densely stellate pubescent; bark of older stems reddish brown with sparse, appressed porrect-stellate trichomes.

Sympodial structure:

Sympodial units plurifoliate

Leaves:

Leaves 9-15 x 3.5-5 cm, elliptic to lanceolate-elliptic, coriaceous, strongly discolorous, the upper surface rugose, scabrous with sessile porrect stellate trichomes with a unicellular midpoint, the lower surface velutinous, grey to yellowish green, the trichomes porrect stellate; base subequal, asymmetric; margins entire; apex acuminate or acute; petiole 1-3 cm long, 2-2.5 mm in diameter, deeply channelled adaxially, pubescent with rusty brown trichomes like those of the stems.

Inflorescences:

Inflorescences internodal, 4-10 cm long, in corymbose cymes, 2-3 times branched, with many flowers, pubescent with stellate trichomes like those of the stems; peduncle 3-5 cm; pedicels 0.4-0.5 cm, longer in fruit, stellate-pubescent like the stems and inflorescence, articulated at the base; pedicel scars unevenly spaced 2-6 mm apart, congested near the tip, slightly raised. Buds ovoid-conical, the corolla partially exserted from the calyx.

Flowers:

Flowers heterostylous, the basal ones long-styled and perfect, the distal ones short-styled and staminate; calyx tube 3-4 mm, campanulate, the lobes 3-5 mm, linear-lanceolate, acute, abaxially tomentose, the trichomes like those of the pedicel but with shorter rays, rusty, adaxially glabrescent with a few stellate trichomes in the distal 1/3; corolla 3-3.5 cm in diameter, purple or deep violet to white, stellate, lobed nearly to the base, the lobes 1-1.2 cm, triangular, reflexed at anthesis, abaxially tomentose with sessile porrect stellate trichomes like those of the pedicel, adaxially glabrous; filament tube minute, the free portion of the filaments 1-2 mm; anthers 7-8 mm, linear-lanceolate, tapering, poricidal at the tips, the pores obverse, not elongating to slits; ovary 1-1.5 mm in diameter, subspherical, tomentose with porrect stellate trichomes with an antrorse multicellular midpoint; style ca. 10 mm in long-styled flowers, straight or curved, puberulent in the basal half, exceeding the anthers in hermaphroditic flowers, shorter and included in staminate flowers; stigma subtruncate, ca. 1.5 mm in diameter.

Fruits:

Fruit a globose berry, 1-1.5 cm in diameter, green or yellowish green, the pericarp pubescent with sessile stellate trichomes; fruiting pedicel 4-6 x 2-2.5 mm, woody and erect.

Seeds:

Seeds 3-3.5 x 2-2.5 mm, flattened reniform, brown, the testa reticulate-undulate.

Chromosome number:

Not known

Distribution:

In lowland forests and forest margins in northern South America, in Surinam, French Guiana and northern Brazil in the Territory of Amapá,

Phenology:

Flowering and fruiting specimens have been collected year-round.

Phylogeny:

Solanum rubiginosum is a member of the Leptostemonum clade (sensu Levin et al., 2006; Weese & Bohs, 2007) based on overall morphology, but its relationships have not yet been tested using molecular data. Whalen (1984) placed it in his S. erythrotrichum group. Agra (2004) places this species in her subsection Rhytidoandrum.

Commentary:

As delimited here Solanum rubiginosum is a distinctive species, easily recognised by its liana (woody vine) habit, appearing erect and shrub-like when young (i.e., von Rohr s.n., the type specimen), adpressed, reddish pubescence and elliptic, coriaceous, discolorous leaves with revolute margins and lustrous, rugose adaxial surfaces. The inflorescences are strictly terminal, the flowers to 3.5 cm in diameter and the fruits reddish with stellate trichomes. Solanum rubiginosum resembles to S. decorum, with which it shares leaf shape, the color of indument and inflorescence type. It differs from that species in its habit, coriaceous leaves with revolute margins and sessile porrect-stellate trichomes, more open inflorescences, larger flowers with purple to deep violet corolla, stellate-pubescent fruits and smaller seeds.

Two specimens of S. rubiginosum were found in the Vahl herbarium in Copenhagen. Of these, C-22914 (F neg. 22914) exactly matches the illustration in Vahl (1798) and is clearly the holotype of this species.

References:

Vahl, M. 1798. Eclogae americanae.
Copenhagen.

Whalen, M.D. 1984. Conspectus of species groups in Solanum subgenus Leptostemonum.
Gentes Herbarum 12 (4): 179-282.

Agra, M.F. 2004. Sinopse Taxonômica de Solanum sect. Erythrotrichum (Solanaceae).
Pages 192-211, in Rangel-Ch, J.O; Aguirre-C, J.; Andrade-C., M.G. & Giraldo-Cañas (Eds). Memorias octavo congreso Latinoamericano Y Segundo Colombiano de Botánica. Instituto de Ciencias Naturales.

Levin, R.A., N.R. Myers, & L. Bohs 2006. Phylogenetic relationships among the "spiny" solanums (Solanum subgenus Leptostemonum).
Amer. J. Bot. 93: 157-169.

Weese, T.L. & L. Bohs 2007. A Three-Gene Phylogeny of the Genus Solanum (Solanaceae)
Syst. Bot. 32(2): 445-463.

Solanaceae Source

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Solanaceae

Solanum rubiginosum Vahl

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