Antirrhinum


Antirrhinum is a genus of plants commonly known as dragon flowers or snapdragons because of the flowers' fancied resemblance to the face of a dragon that opens and closes its mouth when laterally squeezed. They are native to rocky areas of Europe, the United States, and North
Africa.

Description

The genus is morphologically diverse, particularly the New World group. The genus is characterized by personate flowers with an inferior gibbous corolla.

Taxonomy

Antirrhinum used to be treated within the family Scrophulariaceae, but studies of DNA sequences have led to its inclusion in a vastly enlarged family Plantaginaceae within the tribe Antirrhineae.

Circumscription

The taxonomy of this genus is complex and not yet fully resolved at present. In particular the exact circumscription of the genus, especially the inclusion of the New World species, is contentious. The situation is further complicated by the variety of terms in use for infrageneric ranks, especially of the Old World species, that is Antirrhinum, sensu stricto.
The USDA Plants Database recognises only two species: A. majus, the only species naturalised in North America, and A. bellidifolium, now considered to be Anarrhinum bellidifolium Willd. As of April 2017, The Plant List accepts 21 species.
A widely accepted scheme placed 36 species in the genus in three sections. While many botanists accepted this broad circumscription, whose main departure from other classifications was the inclusion of the New World Saerorhinum, others did not, restricting the genus to the Old World. New species also continue to be discovered.
In 2004 research into the molecular systematics of this group and related species by Oyama and Baum confirmed that the genus sensu lato as described by Thompson is monophyletic, provided that one species is removed to the separate genus Pseudorontium, and the two species of Mohavea are included. The species list given here follows these conclusions.
This is the broad circumscription that includes the Old World Misopates and New World Sairocarpus. By contrast the narrow circumscription confines the genus to the monophyletic Old World perennial species with a diploid chromosome number of 16, distributed in the Mediterranean basin, approximately 25 species., following the phylogenetic analysis of Vargas et al. suggesting they are a distinct group. Both Misopates and Sairocarpus are accepted names in The Plant List, and many of the New World species now have Sairocarpus as their accepted name, rather than Antirrhinum. It has been proposed that many of the New World Antirrhinum be now considered under Sairocarpus, in the forthcoming Flora of North America.

Infrageneric subdivision

It is widely agreed that this broad group should be subdivided into three or four subgroups, but the level at which this should be done, and exactly which species should be grouped together, remain unclear. Some authors continue to follow Thompson in using a large genus Antirrhinum, which is then divided into several sections; others treat Thompson's genus as a tribe or subtribe, and divide it into several genera. For a comparison of earlier schemes see Mateu-Andrés and de Paco, Table 1
If the broad circumscription is accepted, its three sections as described by Thompson are as follows :
While Antirrhinum majus is the plant that is usually meant by the term of "snapdragon" if used on its own, many other species in the genus, and in the family Scrophulariaceae more widely, have common names that include the word "snapdragon". Such as Antirrhinum molle is known as "dwarf snapdragon" in the UK.

Species

Etymology

The word "antirrhinum" is derived from the Greek ἀντίρρινον antirrhinon "calf's snout, Antirrhinum Orontium" which in turn is derived from ἀντί anti "against, like", and ῥίς rhis "nose" ; thus, possibly "noselike", possibly referring to the noselike capsule in its mature state.

Ecology

Snapdragons are short-lived perennial plants that survive well in cold seasons but are often replanted each spring and considered annual plants. They do best in full or partial sun, in well-drained soil since their roots are susceptible to rotting. They are classified commercially as a range of heights: midget or dwarf, medium and tall. Removing the dead flowers, also called "deadheading", is important to help them to continuously produce beautiful flowers throughout their growing season. They are susceptible to ethylene gas so removing dead flowers and keeping them away from ripe fruits or vegetables also helps them bloom longer. They grow during their peak seasons of April to June and August to October and bloom in a variety of colors ranging from: white, yellow, orange, red, purple, pink and some multicolored patterns.
They are ecologically diverse, particularly the New World species.

Cultivation

The snapdragon is an important garden plant, widely cultivated from tropical to temperate zones as a bedding, rockery, herbaceous border or container plant. Cultivars have showy white, crimson, or yellow bilabiate flowers. It is also important as a model organism in botanical research, and its genome has been studied in detail.

Genetic studies

Antirrhinum is a genus that has been used from the earliest genetic studies of Gregor Mendel and Charles Darwin and was used as a model by Erwin Baur. Together with closely related genera, it has become a model organism for the investigation of the genetic basis of plant development, particularly floral development.
The genus is a typical example of incomplete dominance by the red allele with the anthocyanin pigment. Any cross between red-flowered and white-flowered snapdragons, give an intermediate and heterozygous phenotype with pink flowers, that carries both the dominant and recessive alleles.
Several species of Antirrhinum are self-incompatible, meaning that a plant cannot be fertilised by its own pollen. Self-incompatibility in the genus has been studied since the early 1900s. Self-incompatibility in Antirrhinum species is controlled gametophytically and shares many important features with self-incompatibility systems in Rosaceae and Solanaceae.

Uses

In addition to growing the plants for cut flowers, the seeds have been used to extract edible oils, particularly in Russia, while the leaves and flowers have been considered to possess antiphlogistic properties and have been used in poultices. A green dye has also been extracted from the flowers.

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