Solanaceae Genera

Solanaceae (), commonly known as the nightshades, is a family of flowering plants in the order Solanales. It contains approximately 2,700 species, several of which are used as agricultural crops, medicinal plants, and ornamental plants. Many members of the family have high alkaloid contents, making some highly toxic, but many—such as tomatoes, potatoes, eggplants, and peppers—are commonly used in food.

Originating in South America, Solanaceae now inhabits every continent on Earth except Antarctica. After the K—Pg extinction event they rapidly diversified and have adapted to live in deserts, tundras, rainforests, plains, and highlands, and taken on wide range of forms including trees, vines, shrubs, and epiphytes. Nearly 80% of all nightshades are included in the subfamily Solanoideae, most of which are members of the type genus ''Solanum''. Most taxonomists recognize six other subfamilies: Cestroideae, Goetzeoideae, Nicotianoideae, Petunioideae, Schizanthoideae, and Schwenkioideae, although nightshade taxonomy is still controversial. The genus ''Duckeodendron'' is sometimes placed in its own subfamily, Duckeodendroideae.

The high alkaloid content in some species has made them valuable for recreational, medicinal, and culinary use. The tobacco plant has been used for centuries as a recreational drug because of its high nicotine content. The tropanes in ''Atropa bella-donna'' can have pain-killing, relaxing, or psychedelic effects, making it a popular plant in alternative medicine, as well as one of the most toxic plants in the world. The presence of capsaicin in ''Capsicum'' species gives their fruits their signature pungency, which are used to make most spicy food products sold today. The potato, tomato, and eggplant, while not usually used for their alkaloids, also have an extensive presence in cuisine. Various food products like ketchup, potato chips, french fries, and multiple regional dishes are extremely commonly eaten around the world. Other nightshades are known for their beauty, such as the long, slender flowers of ''Brugmansia'', the various colors of ''Petunia'', or the spotted and speckled varietes of ''Schizanthus.''

Etymology

The name "Solanaceae" comes from ''Solanum'', the type genus of the family, + '' -aceae'', a standardized suffix for plant family names in modern taxonomy. The etymology of the word ''solanum'' is unclear. The name probably comes from a perceived resemblance of certain species' flowers to the sun ('' sol'' in Latin) and its rays. At least one species of ''Solanum'' is known as the " sunberry". Alternatively, the name could originate from the Latin verb ''solare'', meaning "to soothe", presumably referring to the soothing pharmacological properties of some of the psychoactive species of the family.

The common name "nightshade" developed directly from Middle English '' nyght-shade'', originating from the Old English word '' nihtscada'' ( "shade of night"). Cognates are found in many Germanic languages, such as the German word '' nachtschatten'' and the Dutch word '' nachtschade''. The reason for the usage of the name is ultimately unknown, but it could have been a reference to the appearance of the fruits.

Description

Nightshades can take the form of herbs, shrubs, trees, vines and lianas, and sometimes epiphytes. They can be annuals, biennials, or perennials, upright or decumbent. Some have subterranean tubers. They do not have laticifers, nor latex, nor coloured saps.
They can have a basal or terminal group of leaves or neither of these types. The leaves are generally alternate or alternate to opposed (that is, alternate at the base of the plant and opposed towards the inflorescence). The leaves can be herbaceous, leathery, or transformed into spines. The leaves are generally petiolate or subsessile, rarely sessile. They are frequently inodorous, but some are aromatic or fetid. The foliar lamina can be either simple or compound, and the latter can be either pinnatifid or ternate. The leaves have reticulated venation and lack a basal meristem. The laminae are generally dorsiventral and lack secretory cavities. The stomata are generally confined to one of a leaf's two sides; they are rarely found on both sides.

The flowers are generally hermaphrodites, although some are monoecious, andromonoecious, or dioecious species (such as some ''Solanum'' or ''Symonanthus''). They are most commonly pollinated by insects. The flowers can be solitary or grouped into terminal, cymose, or axillary inflorescences. The flowers are medium-sized, fragrant (''Nicotiana''), fetid (''Anthocercis''), or inodorous. The flowers are usually actinomorphic, slightly zygomorphic, or markedly zygomorphic (for example, in flowers with a bilabial corolla in ''Schizanthus'' species). The irregularities in symmetry can be due to the androecium, to the perianth, or both at the same time. In the great majority of species, the flowers have a differentiated perianth with a calyx and corolla (with five sepals and five petals, respectively) an androecium with five stamens and two carpels forming a gynoecium with a superior ovary (they are therefore referred to as pentamers and tetracyclic). The stamens are epipetalous and are typically present in multiples of four or five, most commonly four or eight. They usually have a hypogynous disk. The calyx is gamosepalous (as the sepals are joined forming a tube), with the (4)5(6) segments equal, it has five lobes, with the lobes shorter than the tube, it is persistent and often accrescent. The corolla usually has five petals that are also joined forming a tube. Flower shapes are typically rotate (wheel-shaped, spreading in one plane, with a short tube) or tubular (elongated cylindrical tube), campanulated, or funnel-shaped.

The androecium has (2)(4)5(6) free stamens within its opposite sepals (they alternate with the petals). They are usually fertile or, in some cases (for example in Salpiglossideae) they have staminodes. In the latter case, there is usually either one staminode (''Salpiglossis'') or three (''Schizanthus''). The anthers touch on their upper end forming a ring, or they are completely free, dorsifixed, or basifixed with poricide dehiscence or through small longitudinal cracks. The stamen's filament can be filiform or flat. The stamens can be inserted inside the coralline tube or exserted. The plants demonstrate simultaneous microsporogenesis, the microspores are tetrad, tetrahedral, or isobilateral. The pollen grains are bicellular at the moment of dehiscence, usually open and angular.

The gynoecium is bicarpelar (rarely three- or five-locular) with a superior ovary and two locules, which may be secondarily divided by false septa, as is the case for Nicandreae and Datureae. The gynoecium is located in an oblique position relative to the flower's median plane. They have one style and one stigma; the latter is simple or bilobate. Each locule has one to 50 ovules that are anatropous or hemianatropous with axillar placentation. The development of the embryo sack can be the same as for ''Polygonum'' or ''Allium'' species. The embryo sack's nuclear poles become fused before fertilization. The three antipodes are usually ephemeral or persistent as in the case of ''Atropa''. The fruit can be a berry as in the case of the tomato or wolfberry, or a dehiscent capsule as in ''Datura'', or a drupe. The fruit has axial placentation. The capsules are normally septicidal or rarely loculicidal or valvate. The seeds are usually endospermic, oily (rarely starchy), and without obvious hairs. The seeds of most Solanaceae are round and flat, about in diameter. The embryo can be straight or curved, and has two cotyledons. Most species in the Solanaceae have 2n=24 chromosomes, but the number may be a higher multiple of 12 due to polyploidy. Wild potatoes, of which there are about 200, are predominantly diploid (2 × 12 = 24 chromosomes), but triploid (3 × 12 = 36 chromosomes), tetraploid (4 × 12 = 48 chromosomes), pentaploid (5 × 12 = 60) and even hexaploid (6 × 12 = 72 chromosome) species or populations exist. The cultivated species ''Solanum tuberosum'' has 4 × 12 = 48 chromosomes. Some ''Capsicum'' species have 2 × 12 = 24 chromosomes, while others have 26 chromosomes.

Diversity of characteristics

Despite the previous description, the Solanaceae exhibit a large morphological variability, even in their reproductive characteristics. Examples of this diversity include: Hunziker, A.T. 1979: South American Solanaceae: a synoptic review. In: D'ARCY, W.G., 1979: The Biology and Taxonomy of the Solanaceae. Linn. Soc. Symp. Ser. 7: p 48-85. Linnean Soc. & Academic Press; London.Balken, J.A. THE PLANT FAMILY SOLANACEAE:
FRUITS IN SOLANACEAE
* The number of carpels that form the gynoecium
In general, the Solanaceae have a gynoecium (the female part of the flower) formed of two carpels. However, ''Melananthus'' has a monocarpelar gynoecium, there are three or four carpels in ''Capsicum'', three to five in '' Nicandra'', some species of '' Jaborosa'' and '' Trianaea'' and four carpels in ''Iochroma umbellatum''.
* The number of locules in the ovary

The number of locules in the ovary is usually the same as the number of carpels. However, some species occur in which the numbers are not the same due to the existence of false septa (internal walls that subdivide each locule), such as in ''Datura'' and some members of the Lycieae (the genera '' Grabowskia'' and ''Vassobia'').
* Type of ovules and their number
The ovules are generally inverted, folded sharply backwards (anatropous), but some genera have ovules that are rotated at right angles to their stalk (campilotropous) as in ''Phrodus'', '' Grabowskia'' or ''Vassobia''), or are partially inverted (hemitropous as in '' Cestrum'', ''Capsicum'', ''Schizanthus'' and ''Lycium''). The number of ovules per locule also varies from a few (two pairs in each locule in ''Grabowskia'', one pair in each locule in ''Lycium'') and very occasionally only one ovule is in each locule as for example in ''Melananthus''.
* The type of fruit
The fruits of the great majority of the Solanaceae are berries or capsules (including pyxidia) and less often drupes.
Berries are common in the subfamilies Cestroideae, Solanoideae (with the exception of ''Datura'', ''Oryctus'', ''Grabowskia'' and the tribe Hyoscyameae) and the tribe Juanulloideae (with the exception of '' Markea'').
Capsules are characteristic of the subfamilies Cestroideae (with the exception of '' Cestrum'') and Schizanthoideae, the tribes Salpiglossoideae and Anthocercidoideae, and the genus ''Datura''. The tribe Hyoscyameae has pyxidia.
Drupes are typical of the Lycieae tribe and in Iochrominae.

Taxonomy

The first scientific reference to Solanaceae was in 1763 in French naturalist Michel Adanson's ''Familles des Plantes''. He did not use a formal name for his taxon, and simply labeled it as "Les Solanum". He included a total of 10 genera, all of which are still accepted as members of the family. Adanson is however not considered to be the authority of the family, that title instead being held by French botanist Antoine Laurent de Jussieu, who gave the group a formal scientific name in 1789 in his '. Jussieu classified the taxon as an order and used the name "Solaneæ". His order included 19 genera, some of which—such as ''Verbascum blattaria'', '' Bontia'', and ''Crescentia cujete''—are no longer considered members of the family. Some genera Jussieu included within Solanaceae he proposed could belong to Boraginaceae, which he also named in ''Genera Plantarum''; he noted that there was a high degree of similarity between Solanaceae and Boraginaceae, and proposed that they could be considered one order.

Following Jussieu's publication, taxonomists have heavily revised, re-examined, and added to the taxon. "Solaneæ" was reclassified as a family by the 1820s, and began to be called "Solanaceae" by some authors around the 1830s, which became the standard name by 1905 per the ICBN nomenclature rules.

In 1835, Gilbert Burnett was the first to publish a subclassification of Solanaceae, and included 4 subgroups: Cestridæ, Nolanidæ, Solanidæ, and Verbascidæ. While Cestridæ and Solanidæ were broadly accepted as subfamilies (later renamed Cestroideae and Solanoideae), Nolanidæ and Verbascidæ, having several non-solanaceous characteristics, were only tentatively assigned to the family by Burnett and eventually were split from the family. While several core genera were widely accepted to be a part of Solanaceae, others have been less stable in their placement. The problem of some species having a mix of solanaceous and non-solanaceous traits continued to be a significant source of conflict in Solanaceae taxnomy. The families Duckeodendraceae, Goetzaceae, and Nolanaceae were particularly tantalizing; it had long been known that they were closely related to Solanceae, but to what extent was unclear. All three families have extremely similar wood anatomy to Solanaceae, and in at least the case of Goetzeaceae leaf anatomy as well.

The advent of molecular phylogenetics in the late 20th century allowed genetic and chemical data to be incorporated into cladistics, providing a new robust method of uncovering evolutionary relationships. An early molecular study by Olmstead et al. in 1999 provided a significant update to Solanaceae taxonomy, splitting Cestroideae into 5 subfamilies, Solaneae into multiple tribes, and finding '' Nolana'' and Geotzeaceae (demoted to subfamily Geotzoideae) to indeed be members of the family. Further studies found Duckeodendraceae to be in the family as well. The contents of the family are now mostly agreed upon, although the exact position of the subgroups is still debated. The December 2024 World Flora Online classification lists 8 subfamilies, 18 tribes, 103 genera, and 2,729 species in the family, shown below.

Subfamily Cestroideae
*''Protoschwenkia'' (1 sp.)
*Tribe Benthamiellae
**'' Benthamiella'' (12 sp.)
**'' Combera'' (2 sp.)
*Tribe Browallieae
**''Browallia'' (22 sp.)
**'' Streptosolen'' (1 sp.)
*Tribe Cestreae
**'' Cestrum'' (172 sp.)
**''Sessea'' (24 sp.)
**'' Vestia'' (1 sp.)
*Tribe Salpiglossideae
**'' Reyesia'' (4 sp.)
**'' Salpiglossis'' (2 sp.)

Subfamily Duckeodendroideae
*''Duckeodendron'' (1 sp.)

Subfamily Goetzeoideae
*'' Coeloneurum'' (1 sp.)
*'' Espadaea'' (1 sp.)
*''Goetzea'' (2 sp.)
*'' Henoonia'' (1 sp.)
*''Metternichia'' (1 sp.)
*'' Tsoala'' (1 sp.)

Subfamily Nicotianoideae
*Tribe Anthocerideae
**''Anthocercis'' (10 sp.)
**''Anthotroche'' (3 sp.)
**''Crenidium'' (1 sp.)
**''Cyphanthera'' (8 sp.)
**''Duboisia'' (4 sp.)
**''Grammosolen'' (4 sp.)
**''Symonanthus'' (2 sp.)
*Tribe Nicotianeae
**''Nicotiana'' (101 sp.)

Subfamily Petunioideae
*Tribe Petunieae
**'' Bouchetia'' (3 sp.)
**''Brunfelsia'' (49 sp.)
**''Calibrachoa'' (29 sp.)
**'' Fabiana'' (16 sp.)
**''Hunzikeria'' (4 sp.)
**'' Leptoglossis'' (6 sp.)
**'' Nierembergia'' (20 sp.)
**'' Petchoa'' (hybrid)
**''Petunia'' (16 sp.)
**'' Plowmania'' (1 sp.)

Subfamily Schizanthoideae
*''Schizanthus'' (16 sp.)

Subfamily Schwenckioideae
*''Heteranthia'' (1 sp.)
*'' Melananthus'' (5 sp.)
*'' Schwenckia'' (20 sp.)

Subfamily Solanoideae
*'' Nectouxia'' (1 sp.)
*'' Salpichroa'' (22 sp.)
*Tribe Capsiceae
**''Capsicum'' (43 sp.)
**''Lycianthes'' (137 sp.)
*Tribe Datureae
**''Brugmansia'' (10 sp.)
**''Datura'' (15 sp.)
**''Trompettia'' (1 sp.)
*Tribe Hyoscyameae
**''Anisodus'' (4 sp.)
**''Atropa'' (1 sp.)
**''Atropanthe'' (1 sp.)
**'' Hyoscyamus'' (17 sp.)
**''Physochlaina'' (7 sp.)
**''Przewalskia'' (1 sp.)
**''Scopolia'' (2 sp.)
*Tribe Jaboroseae
**'' Jaborosa'' (23 sp.)
*Tribe Latueae
**'' Latua'' (1 sp.)
*Tribe Lycieae
**''Lycium'' (93 sp.)
**'' Nolana'' (98 sp.)
**''Sclerophylax'' (12 sp.)
*Tribe Mandragoreae
**'' Mandragora'' (2 sp.)
*Tribe Nicandreae
**''Exodeconus'' (6 sp.)
**'' Nicandra'' (3 sp.)
*Tribe Solandreae
**''Doselia'' (4 sp.)
**''Dyssochroma'' (3 sp.)
**'' Hawkesiophyton'' (3 sp.)
**'' Juanulloa'' (8 sp.)
**'' Markea'' (14 sp.)
**'' Merinthopodium'' (3 sp.)
**'' Poortmannia'' (1 sp.)
**''Schultesianthus'' (8 sp.)
**'' Solandra'' (10 sp.)
**'' Trianaea'' (3 sp.)

Subfamily Solanoideae (cont.)
*Tribe Physalideae
**''Alkekengi'' (1 sp.)
**'' Athenaea'' (14 sp.)
**''Calliphysalis'' (1 sp.)
**''Capsicophysalis'' (1 sp.)
**''Cataracta'' (1 sp.)
**'' Chamaesaracha'' (12 sp.)
**'' Cuatresia'' (19 sp.)
**'' Darcyanthus'' (1 sp.)
**'' Deprea'' (52 sp.)
**'' Discopodium'' (2 sp.)
**'' Dunalia'' (4 sp.)
**'' Eriolarynx'' (4 sp.)
**''Iochroma'' (30 sp.)
**'' Leucophysalis'' (2 sp.)
**''Mellissia'' (1 sp.)
**''Nothocestrum'' (4 sp.)
**'' Orcytes'' (9 sp.)
**'' Pantacantha'' (1 sp.)
**''Physalis'' (84 sp.)
**''Quincula'' (1 sp.)
**''Saracha'' (5 sp.)
**''Schraderanthus'' (1 sp.)
**'' Streptosolen'' (1 sp.)
**'' Trozelia'' (2 sp.)
**'' Tuberowithania'' (1 sp.)
**''Tubocapsicum'' (1 sp.)
**''Tzeltalia'' (3 sp.)
**'' Vassobia'' (2 sp.)
**''Withania'' (9 sp.)
**'' Witheringia'' (19 sp.)
*Tribe Solaneae
**''Jaltomata'' (72 sp.)
**''Solanum'' (1245 sp.)

Evolution

Origin

The early evolution of Solanaceae is poorly understood in part due to the extremely sparse fossil record. Only a few dozen species in the fossil record have been firmly identified as nightshades. Estimates for the origin of the family vary considerably, with molecular clocks ranging from 30.9 to 83.3 million years ago. The oldest fossil nightshades however, ''Physalis hunickenii'' and ''Physalis infinemundi'', firmly place the minimum possible age of the family at 52 million years old. The existence of these fossils indicates that the family is likely significantly older than previously expected. Their position near the base of the tribe Physalideae suggests that Solanaceae had already begun to diversify into its modern lineages by this time.

Using these new fossils, a team in 2023 estimated the age of Solanaceae to be approximately 73.3 million years old. Their work proposed that after the K-Pg mass extinction, the family began to rapidly diversify, with all subfamilies diverging from each other by 56 million years ago. The subfamily Solanoideae was the last to split off from the rest, but experienced the most diversification, and now accounts for 80% of all nightshades. During the Paleocene-Eocene thermal maximum, nearly all solanoid tribal lineages diverged from each other in only about 4 million years.

Dispersion and diversification

Solanaceae originated in South America. It is unique in this regard compared to other families in the order Solanales, which originated primarily in Africa. Its geographic isolation as a result is likely what triggered its initial diversification into a distinct lineage.

From South America, nightshades rapidly colonized the rest of the Americas as they continued to diversify. The spread of nightshades into the Old World happened several times throughout its history. From South America, nightshades spread west over the Pacific into Oceania and east over the Atlantic into Africa. Nightshades reached Eurasia first from North America, and more recently were brought over by humans during the Columbian exchange. In total, there have been about 15-20 natural dispersal events that carried Solanaceae over Earth's oceans. These events could have occurred through various methods, such as seeds being blown through wind currents or floating over the ocean's surface, or carried by migrating animals such as birds.

Phylogeny

The exact relationships within Solanaceae are generally poorly understood. Olmstead et al. (1999) firmly established the contents of the family and outlined its phylogeny: Schwenkioideae, Goetzeoideae, and Schizanthoideae are the most basal, Nicotianoideae and Solanoideae form a well-supported "X=12" clade, and Petunioideae and Cestroideae are closer to the latter than the former. Subfamilial relationships outside the X=12 clade were poorly supported, a problem faced by many future studies as well. A study by Särkinen et al. (2013) with over 1,000 species only found weak support for many clades near the base of the tree. It found that ''Duckeodendron'', ''Schizanthus'' (subfamily Schizanthoideae), and Goetzeoideae were among the most basal, but didn't resolve the relationships between them, and that Cestroideae, Schwenckioideae, and Petunioideae were closer to the well supported "X=12" clade (Nicotianoideae + Solanoideae), albeit with low support. Another large study from Huang et al. (2023) placed ''Schizanthus'' as the most basal of all nightshades, Cestroideae and Schwenkioideae as sisters, and Petunioideae as the sister to the X=12 clade. it had fairly high support for many basal clades in the family compared to previous studies, although were still generally low.

Distribution and habitat

Even though members of the Solanaceae are found on all continents except Antarctica, the greatest variety of species are found in Central America and South America. Centers of diversity also occur in Australia and Africa. Solanaceae occupy a great number of different ecosystems, from deserts to rainforests, and are often found in the secondary vegetation that colonizes disturbed areas. In general, plants in this family are of tropical and temperate distribution.

Ecology

The potato tuber moth ('' Phthorimaea operculella'') is an oligophagous insect that prefers to feed on plants of the family Solanaceae, especially the potato plant (''Solanum tuberosum''). Female ''P. operculella'' use the leaves to lay their eggs and the hatched larvae will eat away at the mesophyll of the leaf. After feeding on the foliage, the larvae will then delve down and feed on the tubers and roots of the plant.

Alkaloids

Hundreds of alkaloids are produced by various species of nightshades, including solanine, chaconine, atropine, tomatine, and several more. These are used as a natural pesticide by the plant, disrupting cellular and physiological processes in invading organisms . They are mainly targeted against insects, but can also function as fungicides, nematicides, and bactericides. In high amounts, some alkaloids can also be toxic to humans, but others are sought after for medicinal, recreational, or culinary purposes.

Solanine

Solanine is a toxic glycoalkaloid with a bitter taste, it has the formula C₄₅H₇₃NO₁₅. It is formed by the alkaloid solanidine with a carbohydrate side chain. It is found in leaves, fruit, and tubers of various Solanaceae such as the potato and tomato. Its production is thought to be an adaptive defence strategy against herbivores. Substance intoxication from solanine is characterized by gastrointestinal disorders (diarrhoea, vomiting, abdominal pain) and neurological disorders (hallucinations and headache). The median lethal dose is between 2 and 5 mg/kg of body weight. Symptoms manifest 8 to 12 hours after ingestion. The amount of these glycoalkaloids in potatoes, for example, varies significantly depending on environmental conditions during their cultivation, the length of storage, and the variety. The average glycoalkaloid concentration is 0.075 mg/g of potato.Zeiger, E. 1998. Solanine and Chaconine. Review of Toxicological Literature. Integrated Laboratory Systems, USA. Solanine has occasionally been responsible for poisonings in people who ate berries from species such as ''Solanum nigrum'' or ''Solanum dulcamara'', or green potatoes.

Tropanes

The term "tropane" comes from the genus ''Atropa'', named after the Greek Fate, Atropos, who cut the thread of life. This nomenclature reflects its toxicity and lethality. They are bicyclic organic nitrogen compounds (IUPAC nomenclature: 8-methyl-8-azabicyclo .2.1ctane), with the chemical formula of C₈H₁₅N. These alkaloids include, among others, atropine, cocaine, scopolamine, and hyoscyamine. They are found in various species, such as mandrake (''Mandragora officinarum'' and M. autumnalis ), black henbane or stinking nightshade (''Hyoscyamus niger''), belladonna (''Atropa belladonna''), jimson weed or devil's snare (''Datura stramonium'') and ''Brugmansia'' , as well as many others in the family Solanaceae. Pharmacologically, they are the most powerful known anticholinergics in existence, meaning they inhibit the neurological signals transmitted by the endogenous neurotransmitter, acetylcholine. More commonly, they can halt many types of allergic reactions. Symptoms of overdose may include dry mouth, dilated pupils, ataxia, urinary retention, hallucinations, convulsions, coma, and death. Atropine, a commonly used ophthalmological agent, dilates the pupils and thus facilitates examination of the interior of the eye. In fact, juice from the berries of ''A. belladonna'' were used by Italian courtesans during the Renaissance to exaggerate the size of their eyes by causing the dilation of their pupils ("bella donna" means "pretty woman" in Italian). Despite the extreme toxicity of the tropanes, they are useful drugs when administered in extremely small dosages. They can reverse cholinergic poisoning, which can be caused by overexposure to organophosphate insecticides and chemical warfare agents such as sarin

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