Solanaceae


The Solanaceae, or nightshades, are a family of flowering plants that ranges from annual and perennial herbs to vines, lianas, epiphytes, shrubs, and trees, and includes a number of agricultural crops, medicinal plants, spices, weeds, and ornamentals. Many members of the family contain potent alkaloids, and some are highly toxic, but many—including tomatoes, potatoes, eggplant, bell and chili peppers—are used as food. The family belongs to the order Solanales, in the asterid group and class Magnoliopsida. The Solanaceae consists of about 98 genera and some 2,700 species, with a great diversity of habitats, morphology and ecology.
The name Solanaceae derives from the genus Solanum, "the nightshade plant". The etymology of the Latin word is unclear. The name may come from a perceived resemblance of certain solanaceous flowers to the sun 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 family has a worldwide distribution, being present on all continents except Antarctica. The greatest diversity in species is found in South America and Central America. In 2017, scientists reported on their discovery and analysis of a fossil tomatillo found in the Patagonian region of Argentina, dated to 52 million years B.P. The finding has pushed back the earliest appearance of the plant family Solanaceae. As tomatillos likely developed later than other nightshades, this may mean that the Solanaceae may have first developed during the Mesozoic Era.
The Solanaceae include a number of commonly collected or cultivated species. The most economically important genus of the family is Solanum, which contains the potato, the tomato, and the eggplant or aubergine . Another important genus, Capsicum, produces both chili peppers and bell peppers.
The genus Physalis produces the so-called groundcherries, as well as the tomatillo, the Cape gooseberry and the Chinese lantern. The genus Lycium contains the boxthorns and the wolfberry Lycium barbarum. Nicotiana contains, among other species, tobacco.
Some other important members of Solanaceae include a number of ornamental plants such as Petunia, Browallia, and Lycianthes, and sources of psychoactive alkaloids, Datura, Mandragora, and Atropa belladonna. Certain species are widely known for their medicinal uses, their psychotropic effects, or for being poisonous.
Most of the economically important genera are contained in the subfamily Solanoideae, with the exceptions of tobacco and petunia.
Many of the Solanaceae, such as tobacco and petunia, are used as model organisms in the investigation of fundamental biological questions at the cellular, molecular, and genetic levels.

Etymology and pronunciation

The name "Solanaceae" comes to international scientific vocabulary from New Latin, from Solanum, the type genus, + ', a standardized suffix for plant family names in modern taxonomy. The genus name comes from the Classical Latin word ', referring to nightshades, "probably from, 'sun', + ', neuter of '."

Description

Plants in the Solanaceae 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. 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. Pollination is entomophilous. The flowers can be solitary or grouped into terminal, cymose, or axillary inflorescences. The flowers are medium-sized, fragrant, fetid, or inodorous. The flowers are usually actinomorphic, slightly zygomorphic, or markedly zygomorphic. 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 an androecium with five stamens and two carpels forming a gynoecium with a superior ovary. 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, with the 5 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 together forming a tube. Flower shapes are typically rotate or tubular, campanulated or funnel-shaped.
The androecium has 5 free stamens within it, oppositsepals, they are usually fertile or, in some cases they have staminodes. In the latter case, there is usually either one staminode or three. 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 filliform 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 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 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, 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, but triploid, tetraploid, pentaploid and even hexaploid 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:
In general, the Solanaceae have a gynoecium 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 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, such as in Datura and some members of the Lycieae.
The ovules are generally inverted, folded sharply backwards, but some genera have ovules that are rotated at right angles to their stalk, or are partially inverted. The number of ovules per locule also varies from a few and very occasionally only one ovule is in each locule as for example in Melananthus.
The fruits of the great majority of the Solanaceae are berries or capsules and less often drupes.
Berries are common in the subfamilies Cestroideae, Solanoideae and the tribe Juanulloideae.
Capsules are characteristic of the subfamilies Cestroideae 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.

Alkaloids

s are nitrogenous organic substances produced by plants as a secondary metabolite and which have an intense physiological action on animals even at low doses. Solanaceae are known for having a diverse range of alkaloids. To humans, these alkaloids can be desirable, toxic, or both. The tropanes are the most well-known of the alkaloids found in the Solanaceae. The plants that contain these substances have been used for centuries as poisons. However, despite being recognized as poisons, many of these substances have invaluable pharmaceutical properties. Many species contain a variety of alkaloids that can be more or less active or poisonous, such as scopolamine, atropine, hyoscyamine, and nicotine. They are found in plants such as henbane, belladonna, jimson weed, mandrake, tobacco, and others. Some of the main types of alkaloids are:

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.

Plant host

The potato tuber moth is an oligophagous insect that prefers to feed on plants of the family Solanaceae, especially the potato plant. 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.

Taxonomy

The following taxonomic synopsis of the Solanaceae, including subfamilies, tribes and genera, is based on the most recent molecular phylogenetics studies of the family:

Cestroideae (Browallioideae)

This subfamily is characterised by the presence of pericyclic fibres, an androecium with four or five stamens, frequently didynamous. The basic chromosome numbers are highly variable, from x=7 to x=13. The subfamily consists of eight genera and about 195 species distributed throughout the Americas. The genus Cestrum is the most important, as it contains 175 of the 195 species in the subfamily. The Cestreae tribe is unusual because it includes taxa with long chromosomes, when the rest of the family generally possesses short chromosomes
This subfamily is characterized by the presence of drupes as fruit and seeds with curved embryos and large fleshy cotyledons. The basic chromosome number is x=13. It includes four genera and five species distributed throughout the Greater Antilles. Some authors suggest their molecular data indicate the monotypic genera Tsoala Bosser & D'Arcy should be included in this subfamily, endemic to Madagascar, and Metternichia to the southeast of Brazil. Goetzeaceae Airy Shaw is considered as a synonym of this subfamily.
Molecular phylogenetics indicates that Petunioideae is the sister clade of the subfamilies with chromosome number x=12. They contain calistegins, alkaloids similar to the tropanes. The androecium is formed of four stamens, usually with two different lengths. The basic chromosome number of this subfamily can be x=7, 8, 9 or 11. It consists of 13 genera and some 160 species distributed throughout Central and South America. Molecular data suggest the genera originated in Patagonia. Benthamiella, Combera, and Pantacantha form a clade that can be categorized as a tribe that should be in the subfamily Goetzeoideae.
The Schizanthoideae include annual and biennial plants with tropane alkaloids, without pericyclic fibres, with characteristic hair and pollen grains. The flowers are zygomorphic. The androecium has two stamens and three staminodes, anther dehiscence is explosive. In terms of fruit type, the Schizanthoidae retain the plesiomorphic fruit form of the family Solanaceae, capsules, which rely on an anemochorous, abiotic form of dispersal. This is present in Schizanthoidae due both to the genetic constraints of early divergence as well as Schizanthus evolution and presence in open habitats.
The embryo is curved. The basic chromosome number is x=10. Schizanthus is a somewhat atypical genus among the Solanaceae due to its strongly zygomorphic flowers and basic chromosome number. Morphological and molecular data suggest Schizanthus is a sister genus to the other Solanaceae and diverged early from the rest, probably in the late Cretaceous or in the early Cenozoic, 50 million years ago. The great diversity of flower types within Schizanthus has been the product of the species’ adaptation to the different types of pollinators that existed in the Mediterranean, high alpine, and desert ecosystems then present in Chile and adjacent areas of Argentina.
Annual plants with pericyclic fibres, their flowers are zygomorphic, the androecium has four didynamous stamens or three staminodes; the embryo is straight and short. The basic chromosome number is x=12. It includes four genera and some 30 species distributed throughout South America.
The following genera have not yet been placed in any of the recognized subfamilies within the solanaceas.
The Solanaceae contain 98 genera and some 2,700 species. Despite this immense richness of species, they are not uniformly distributed between the genera. The eight most important genera contain more than 60% of the species, as shown in the table below. Solanum – the genus that typifies the family - includes nearly 50% of the total species of the solanaceas.
GeneraApproximate number of species
Solanum1,330
Lycianthes200
Cestrum150
Nolana89
Physalis85
Lycium85
Nicotiana76
Brunfelsia45
Estimated number of species in the family2,700

Economic importance

The family Solanaceae contains such important food species as the potato, the tomato, the pepper and the aubergine or egg plant. Nicotiana tabacum, originally from South America, is now cultivated throughout the world to produce tobacco.
Many solanaceas are important weeds in various parts of the world. Their importance lies in the fact that they can host pathogens or diseases of the cultivated plants, therefore their presence increases the loss of yield or the quality of the harvested product. An example of this can be seen with Acnistus arborescens and Browalia americana that host thrips, which cause damage to associated cultivated plants, and certain species of Datura that play host to various types of virus that are later transmitted to cultivated solanaceas. Some species of weeds such as, Solanum mauritianum in South Africa represent such serious ecological and economic problems that studies are being carried out with the objective of developing a biological control through the use of insects.
A wide variety of plant species and their cultivars belonging to the Solanaceae are grown as ornamental trees, shrubs, annuals and herbaceous perennials Examples include Brugmansia x candida grown for its large pendulous trumpet-shaped flowers, or Brunfelsia latifolia, whose flowers are very fragrant and change colour from violet to white over a period of 3 days. Other shrub species that are grown for their attractive flowers are Lycianthes rantonnetii with violet-blue flowers and Nicotiana glauca Other solanaceous species and genera that are grown as ornamentals are the petunia , Lycium, Solanum, Cestrum, Calibrachoa × hybrida and Solandra. There is even a hybrid between Petunia and Calibrachoa that is being sold as an ornamental. Many other species, in particular those that produce alkaloids, are used in pharmacology and medicine ''.

Solanaceae and the genome

Many of the species belonging to this family, among them tobacco and the tomato, are model organisms that are used for research into fundamental biological questions. One of the aspects of the solanaceas’ genomics is an international project that is trying to understand how the same collection of genes and proteins can give rise to a group of organisms that are so morphologically and ecologically different. The first objective of this project was to sequence the genome of the tomato. In order to achieve this each of the 12 chromosomes of the tomato’s haploid genome was assigned to different sequencing centres in different countries. So chromosomes 1 and 10 were sequenced in the United States, 3 and 11 in China, 2 in Korea, 4 in Britain, 5 in India, 7 in France, 8 in Japan, 9 in Spain and 12 in Italy. The sequencing of the mitochondrial genome was carried out in Argentina and the chloroplast genome was sequenced in the European Union.