Solanum
Solanum is a genus of herbaceous, shrubby or climbing plants. The type genus of the family Solanaceae. Contains edible and cultivated species, including potatoes, tomatoes and eggplants.
Description
Solanum includes herbaceous plants, shrubs, trees or lianas, with or without thorns, glabrous or pubescent, with branched or simple hairs, frequently glandular.
In most species, the stem is aerial, circular, or angular in cross section. However, there is a group of species within the genus (the Petota section) that also has two types of underground stems: rhizomes and tubers, which is why they are known as tuberous species of solanum. The rhizomes are formed by more or less long lateral shoots that arise from the base of the aerial stem. They grow alternately from subnodes located on the aerial stems and have horizontal growth under the soil surface. Each rhizome, meanwhile, through a thickening at its distal end, generates a tuber. These tubers function as a nutrient storage organ. The tubers are covered by an ectoderm that appears when the epidermis breaks, which thickens over time. On its surface there are "eyes", depressions to protect the vegetative buds that originate the aerial stems, which are arranged in a helical fashion. In addition, there are holes that allow breathing, called lenticels. The lenticels are circular and their number varies by unit area, tuber size, and environmental conditions. The tubers can be elongated, rounded, or oblong in shape; its color, meanwhile, can be white, yellow, violet or reddish.
The leaves are alternate or paired, simple to pinate-shaped or compound, stalked or sessile, without stipules. The inflorescence is a top.
Flowers are usually hermaphroditic, actinomorphic or zygomorphic, formed by four cycles of floral parts, each consisting of five members. The calyx is bell-shaped, often growing in the fruit. The corolla is rotated, bell-shaped, stellate, or urceolate. The color of the corolla can be white, green, yellow, pink, or purple. The stamens can be the same or unequal, the filaments are generally short and inserted at the base of the corolla. The anthers are basifixed and open through terminal pores that often expand into longitudinal openings. They require pollination by buzz. The ovary is bi-carpellate, with numerous ovules. The style is articulated at the base, the stigma is capitate. The fruit is a berry, generally globose and fleshy, sometimes ovoid or ellipsoid, but occasionally dry, with many flat seeds. The seeds are surrounded by a mucilaginous substance that prevents germination.
The embryo is curved and the endosperm is abundant. The basic chromosome number is x=12 and 23.
Alkaloids
The plants of this genus are rich in alkaloids (for example solanine), potentially dangerous for those who consume them.
Distribution
Solanum is one of the largest genera of Angiosperms, with at least 1250 species, and is comparable in size to Senecio, Astragalus and Carex. It is distributed worldwide, with the highest concentration of species in the tropics and subtropics. However, most Solanum species are native to South America, especially in the Andes. Secondary centers of diversity and endemism exist in North America, Central America, eastern Brazil, the West Indies, Australia, Africa, and Madagascar.
Taxonomy
The genus was created by Joseph Pitton de Tournefort and published in Institutiones Rei Herbariae..., Editio tertia [...] Tomus primus, Class II, Sectio VII, Genus I, p. 148[2], Tomus II, tab. 62[3], 1719; it was validated, more than 30 years later, by Carlos Linnaeus and published in Species Plantarum, vol. 1 p. 184[4], 1753 and its expanded description in Genera Plantarum, no. 224, p. 85 [5], 1754.
Etymology
- Solanum: Latin word equivalent to Greek στρ・χνος (strychnos) to designate Solanum nigrum (the "Hierba mora") — and probably other species of the genus, including the eggplant — already employed by Plinius the Old in his Natural history (21, 177 and 27, 132) and, before, by Aulus Cornelius Celsus in Re Medica (II, 33). It could be related to Latin Sun., "the sun", because the plant would be of some sunny sites.
With a number of some 1250-1700 valid species registered (almost 6500 adding the synonyms, nomen nudum, etc...) Solanum is the most common genus rich in species of the Solanaceae family and one of the largest of the Angiosperms. Phylogenetic analyzes of molecular data have made it possible to establish or confirm that the genera Lycopersicon, Cyphomandra, Normania, and Triguera, previously considered independent, should actually be included within Solanum. In fact, all species in those 4 genera have been formally transferred to Solanum.
In contrast, the genus Lycianthes, sometimes considered within Solanum, has been shown to be a separate genus.
Within the Solanaceae family, Solanum is included in the Solanoideae subfamily, characterized by its flat seeds and curved embryos. Within this subfamily, Solanum is arranged in the taxonomically complex tribe Solaneae, a large group of approximately 34 genera, whose phylogenetic relationships are not yet fully elucidated.
According to the widely accepted scheme of D'Arcy which is based on the morphology of the species of the genus, Solanum comprises 7 subgenera and approximately 60 to 70 sections:
- Solanum subg. Archaesolanum Marzell
- Solanum subg. Bassovia (Aubl.) Bitter
- Solanum subg. Leptostemonum (Dunal) Bitter
- Solanum subg. Lyiosalanum Bitter
- Solanum subg. Minon Raf.
- Brevantherum Sections, Holophylla
- Solanum subg. Potatoe (G. Don) D'Arcy
- Sections: Petota, Neolycopersicon, Dulcamara, Glaucophyllum, Basarthrum, Jasminosolanum, Rhychantherum
- Solanum subg. Solanum
- Sections Quadrangulare, Benderianum, Afro-olanum, Lemurisolanum, Macroniotes, Solanum, Episarcophyllum, Delitescen, Capanulisolanum, Geminata, Pseudocapsicum, Chamaesarachidium
Synonymy
Species
The species of the genus Solanum, due to their high number, have been listed in the Solanum species annex.
Economic and cultural importance
Many species of the genus have tubers and constitute the most economically important group. Most of these species are essential for future potato breeding programs because they are resistant to low temperatures, insects, viruses, and fungi; Half of the potato varieties grown in some European countries contain germplasm of the Mexican wild potato Solanum demissum. Solanum is a genus of global economic importance as it includes important crops such as potato (Solanum tuberosum), tomato (Solanum lycopersicum) and eggplant (Solanum melongena).
There are also several species cultivated on a smaller scale for their edible fruits, tubers or leaves and also as a source of valuable medicinal alkaloids. Some examples of lesser-known species cultivated for their edible fruits are the “tree tomato” (Solanum betaceum), the “naranjilla” (Solanum quitoense) and the “pepino » (Solanum muricatum), native to the New World, and Solanum aethiopicum and Solanum macrocarpon from the Old World.