Solanum glaucophyllum Desf.

Solanum glaucophyllum can distinguished from other species in the section by its usually glabrous, glaucous, lanceolate to elliptic leaves with decurrent bases and short, slightly winged petioles, its rotate-stellate corolla with a relatively long tube and broad lobes, and its globose, purple-black, glaucous fruits. The stems are smooth and usually light yellowish or whitish, and the leaf midribs and margins are often thickened, inrolled, and whitish or cream-colored. Throughout its range, S. glaucophyllum exhibits great morphological variability, especially in leaf shape, which ranges from elliptic to nearly linear, and in corolla and fruit size. Narrow-leaved plants generally have smaller flowers and fruits than those with broader leaves, and narrow-leaved forms seem more common in the northern part of the geographical range of this species.

This species grows commonly in flooded or swampy ground, where it forms thickets, known as “varillales” or “duraznillales”, of virgate stems from spreading rhizomes (Cabrera & Zardini, 1978; Okada et al., 1977). It is reportedly deciduous in winter (Okada et al., 1977). The fruits apparently float readily and may be dispersed by water (Nee 37532); they are also eaten by birds (Gibson s.n.).

Solanum glaucophyllum is of economic importance mainly because it causes a disease, “enteque seco” or “espichamento,” of grazing animals (D’Arcy, 1974; Morris, 1977; Okada et al., 1977; Wasserman, 1974). The disease is characterized by calcification of soft tissues, frequently leading to death, and has caused losses of millions of dollars annually to livestock ranchers in Argentina (Cabrera, 1983). The active principle of S. glaucophyllum has been shown to be a vitamin D-like substance that increases calcium and phosphorous absorption (Morris, 1977; Wasserman, 1974). Extracts of S. glaucophyllum are currently being tested for activity as bone growth factors useful in human and veterinary medicine (Morris, 1977; B. Barr, pers. comm.).

Solanum glaucophyllum is most similar to S. confusum of northwestern Argentina and adjacent Bolivia, and to S. matadori of southeastern Brazil. Solanum confusum differs from S. glaucophyllum in being frequently pubescent, and by having leaves with longer petioles, shorter corolla tubes with narrower corolla lobes, and yellow to orange fruits. Solanum matadori is glabrous like most plants of S. glaucophyllum, but it has stellate corollas, green rather than glaucous leaves, and is known only from Santa Catarina, Brazil.

On the basis of morphological characters, Child (1986) considered S. glaucophyllum to be unrelated to section Cyphomandropsis. He removed it to its own section, Solanum section Glaucophyllum Child, included within Solanum subgenus Solanum. Dottori (1995) investigated fruit and seed morphology of this species and concluded that there were significant differences in fruit and seed characters between S. glaucophyllum and the other species of section Cyphomandropsis (S. confusum, S. fusiforme, and S. stuckertii) she investigated. These differences included epicuticular wax covering the fruit exocarp, ventilation cracks rather than stomata in the fruit surface, and seed coat cells with a distinct shape and pattern of wall thickening. While S. glaucophyllum exhibits some unique characters and may represent an isolated clade within the section, its tapered anthers, large angled seeds, and large chromosomes establish it as a member of section Cyphomandropsis. Molecular data from chloroplast and nuclear sequences confirm that S. glaucophyllum belongs to the Cyphomandra clade (Bohs, in press a, b).

A few collections (Arenas 1407, Döbereiner & Tokarnia 794, 797, 800, Hatschbach & Guimarães 21941, Schaller 301) from ca. 20°S latitude in the Río Paraguay drainage are anomalous in being moderately to densely puberulent-pubescent on the axes and leaves. The pubescent plants were recognized as a separate variety by C. V. Morton, but under an unpublished herbarium name. Because they conform to typical S. glaucophyllum in all other respects and occur within the range of the glabrous forms, I do not consider them to be taxonomically distinct.

Solanum glaucophyllum has often been confused with S. amygdalifolium Steud. (also known under the synonyms S. angustifolium Lam., S. persicifolium Mart., S. handelianum Morong, S. brittonianum Morong), which is sympatric and is found in similar habitats. Solanum amygdalifolium, however, is a twining or scandent vine with strongly ridged stems and ovate-lanceolate leaves. The anthers dehisce by broad pores that open into longitudinal slits, and the seeds are much smaller than those of S. glaucophyllum. Solanum amygdalifolium belongs to the dulcamaroid group of Solanum (sects. Dulcamara, Jasminosolanum and relatives; Dulcamaroid clade sensu Bohs, in press a) and, though strikingly convergent in several morphological features, is not closely allied to section Cyphomandropsis.

Desfontaines (1829) published the name S. glaucophyllum in reference to a plant in cultivation in the Paris Botanic Garden. I was unable to locate a type specimen for this name, and a search of the collections at P by Sandra Knapp in 1998 failed to turn up any candidates. D’Arcy (1974) cited a specimen at MPU labelled as “S. glaucophyllum Hort. Paris Cat. Ann. 1829, p. 396” and speculated that it may be a type. Sandra Knapp in 1998 found this specimen at MPU, but with the additional annotation “h.m. Jul 1840,” indicating that it was grown at the Montpellier Botanic Garden in 1840 and thus cannot be a type. Specimens from BR, FI, and G attest to the cultivation of this species in the Paris Botanic Garden in the early nineteenth century. Dunal (1852) indicates that both the names S. glaucophyllum and S. glaucum were in use to refer to this species. It is likely that S. glaucophyllum was described from living material, and that no type specimen exists. Desfontaines original description is adequate to establish the name of this taxon.

Later authors Kuntze (1898), Chodat (1916), and Hassler (1918) proposed a number of infraspecific taxa based on leaf color and size. All of these taxa are subsumed within the range of variation that are encompassed in my concept of the species.

Solanum glaucophyllum was cultivated in French botanical gardens at Angers, Hyeres, and Dijon in the mid-nineteenth and early twentieth century, and specimens are also known from Japan, Nepal, and the United States (Pensacola, Florida). It is not known whether the Asian plants were cultivated or adventive, but probably at least the Nepal collection was a deliberate introduction. D’Arcy (1974) speculates that S. glaucophyllum was introduced to Florida in ships’ ballast. It has not been collected from Florida since 1901.