Prunus
Prunus is a genus of trees and shrubs, including the plums, cherries, peaches, apricots and almonds. It is traditionally placed within the rose family Rosaceae as a subfamily, the Prunoideae (or Amygdaloideae), but sometimes placed in its own family, the Prunaceae (or Amygdalaceae). There are around 430 species of Prunus, spread throughout the northern temperate regions of the globe.
The flowers are usually white to pink, with five petals and five sepals. They are borne singly, or in umbels of two to six or more on racemes. The fruit of all Prunus species is a drupe with a relatively large "stone". Leaves are simple and usually lanceolate, unlobed and toothed along the margin.
Classification
Historical
The first use of prunus as a genus name belongs to Linnaeus in Hortus Cliffortianus of 1737, which went on to become Species Plantarum. In that work Linnaeus attributes the word to "Varr.", who must be Marcus Terentius Varro. The word is not very frequent in Latin. Pliny uses prunus silvestris to mean the blackthorn.
The Online Etymological Dictionary presents the customary derivations of plum and prune from Latin prunum, the plum, which is frequent in a number of authors, including Pliny. The word is not native Latin, but is a loan from Greek prounos, from proumnos, origin unknown. Most dictionaries follow Hoffman, Etymologisches Wörterbuch des Grieschischen, in making it a loan from a pre-Greek language of Asia Minor, related to Phrygian.
This view can be botanically misleading. The origin of the word is not the origin of the tree. A possible classical importation of some plum cultivated in Asia Minor does not mean that species classified under Prunus today were not in ancient Greece and Italy.
In 1737 Linnaeus used four genera to capture modern Prunus: Amygdalus, Cerasus, Prunus and Padus, but simplified to Amygdalus and Prunus in 1758. Since then various genera of Linnaeus and others have become subgenera and sections, as it clearer that all the Prunus species are more closely related. Liberty Hyde Bailey says:
- "The numerous forms grade into each other so imperceptibly and inextricably that the genus cannot be readily broken up into species."[1]
Modern
A recent DNA study of 48 species of Prunus concluded that Prunus is monophyletic and is descended from some Eurasian ancestor.[2]
Historical treatments break the genus up into several different genera, but this segregation is not currently widely recognised other than at the subgeneric rank. ITIS recognises just the single Genus Prunus, with an open list of species,[3] all of which are shown in the box on the right.[4]
One standard contemporaneous treatment of subgenera derives from the work of Alfred Rehder in 1940. Rehder hypothesized five subgenera: Amygdalus, Prunus, Cerasus, Padus and Laurocerasus.[5] To them C. Ingram added Lithocerasus.[6] The six contemporaneous subgenera are described as follows:
- Prunus subgenera:
- Subgenus Amygdalus: almonds and peaches. Axillary buds in threes (vegetative bud central, two flower buds to sides). Flowers in early spring, sessile or nearly so, not on leafed shoots. Fruit with a groove along one side; stone deeply grooved. Type species Prunus dulcis (Almond).
- Subgenus Prunus: plums and apricots. Axillary buds solitary. Flowers in early spring stalked, not on leafed shoots. Fruit with a groove along one side; stone rough. Type species Prunus domestica (Plum).
- Subgenus Cerasus: cherries. Axillary buds single. Flowers in early spring in corymbs, long-stalked, not on leafed shoots. Fruit not grooved; stone smooth. Type species Prunus cerasus (Sour cherry).
- Subgenus Lithocerasus: dwarf cherries. Axillary buds in threes. Flowers in early spring in corymbs, long-stalked, not on leafed shoots. Fruit not grooved; stone smooth. Type species Prunus pumila (Sand cherry).
- Subgenus Padus: bird cherries. Axillary buds single. Flowers in late spring in racemes on leafy shoots, short-stalked. Fruit not grooved; stone smooth. Type species Prunus padus (European bird cherry).
- Subgenus Laurocerasus: cherry-laurels. Axillary buds single. Flowers in early spring in racemes, not on leafed shoots, short-stalked. Fruit not grooved; stone smooth. Mostly evergreen (all the other subgenera are deciduous). Type species Prunus laurocerasus (European cherry-laurel).
Another recent DNA study[5] found that Amygdaloideae can be divided into two clades: Prunus-Maddenia, with Maddenia basal within Prunus, and Exochorda-Oemleria-Prinsepia. Prunus can be divided into two clades: Amygdalus-Prunus and Cerasus-Laurocerasus-Padus. Yet another study adds Empectocladus as a subgenus to the former.[7]
Uses
The genus Prunus includes the almond, apricot, cherry, peach and plum, all of which have cultivars developed for commercial fruit production. The edible part of the almond is the seed; the almond fruit is a drupe and not a "nut". There are also a number of species, hybrids, and cultivars grown strictly as ornamental plants, usually for their profusion of flowers, occasionally for leaves and bark. These ornamentals include the group that may be collectively called flowering cherries.
Pygeum is a herbal remedy containing extracts from the bark of Prunus africana. It is used as to alleviate some of the discomfort caused by inflammation in patients suffering from benign prostatic hyperplasia.
Because of their considerable value as both food and ornamental plants, many Prunus species have been introduced to parts of the world to which they are not native. Many of the Old World species are grown for ornament or fruit, and have been planted throughout the world; and some have become naturalised beyond their native range.
Prunus species are used as food plants for the larvae of a large number of Lepidoptera species.
.
Palaeobotanical models
The earliest fossil Prunus are wood, drupe and seed and a leaf from the middle Eocene of the Princeton Chert of British Columbia.[8] Using the known age as calibration data, recent research by Oh and Potter[9] reconstructs a partial phylogeny of some Rosaceae from a number of nucleotide sequences. According to this study Prunus and its "sister clade" Maloideae (apple subfamily) diverged at 44.3 mya (well before most of the Primates existed). This date is within the Lutetian, or older middle Eocene.[10] Stokey and Wehr report:[8] "The Eocene was a time of rapid evolution and diversification in Angiosperm families such as the Rosaceae ...."
The Princeton finds are among a large number of Angiosperm fossils from the Okanagan Highlands dating to the late early and middle Eocene. Crataegus is found at three locations: Mcabee, Republic and Princeton, while Prunus is found at those locations and Quilchena and Chuchua. A recent recapitulation of research on the topic[11] reports that the Rosaceae were more diverse at higher altitudes. The Okanagan formations date to as early as 52 mya, but the 44.3 mya data, which is approximate, depending on assumptions, might still apply. The authors assert: "... the McAbee flora records a diverse early middle Eocene angiosperm-dominated forest."[12]
Notes
- ^ Bailey, page 181.
- ^ Bortiri and others.
- ^ Do a search in the ITIS database on the scientific name Prunus for its current list.
- ^ Other established species appear in the box as well, which for whatever reasons are not yet in ITIS.
- ^ a b Sangtae Lee and Jun Wen, A phylogenetic analysis of Prunus and the Amygdaloideae (Rosaceae) using ITS sequences of nuclear ribosomal DNA, American Journal of Botany. 2001;88:150-160. This article summarizes the classification of Prunus and gives additional data derived from chemical analysis. It may be found online at [1].
- ^ Stone Fruits, article by William Okie submitted to the Encyclopedia of Fruits and Nuts in July 2003. Summary and Abstract are available at [2], a USDA Reasearch site.
- ^ Bortiri, Esteban (2002). "The Phylogenetic Utility Of Nucleotide Sequences Of SORBITOL 6-PHOSPHATE DEHYDROGENASE In Prunus (Rosaceae)" (PDF). American Journal of Botany. 89 (11): 1697–1708.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) The specification is Emplectocladus (Torr.) Sargent - ^ a b Stockey & Wehr (1996) pages 241 and 245.
- ^ Oh, Sang-Hun (2005). "Molecular phylogenetic systematics and biogeography of tribe Neillieae (Rosaceae) using DNA sequences of cpDNA, rDNA, and LEAFY1". American Journal of Botany. 92: pages 179-192.
{{cite journal}}:|pages=has extra text (help); Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ A date of 76 mya is given for Rosaceae, which is within the late Cretaceous.
- ^ Dillhoff, Richard M (February 2005). "The McAbee flora of British Columbia and its relation to the Early-Middle Eocene Okanagan Highlands flora of the Pacific Northwest" (PDF). Canadian Journal of Earth Sciences. 42 (2): pages 151-166.
{{cite journal}}:|pages=has extra text (help); Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ Page 165.
Bibliography
- Bailey, Liberty Hyde (1898). Sketch of the Evolution of Our Native Fruits. New York: The MacMillan Company.
- Bortiri, Esteban; et al. (2001), "Phylogeny and Systematics of Prunus (Rosaceae) as Determined by Sequence Analysis of ITS and the Chloroplast trnL-trnF Spacer DNA", Systematic Botany, 26 (4): pages 797-807
{{citation}}:|pages=has extra text (help); Explicit use of et al. in:|last=(help). Abstract and first page for free. - Linnaeus Carolus; Sprengel, Curtius (editor) (1830). Genera Plantarum Editio Nona. Gottingen: Dieterich.
{{cite book}}:|author=has generic name (help)CS1 maint: multiple names: authors list (link) For Prunus see page 403. - Stockey, Ruth A.; Wesley C., Wehr (1996), "Flowering Plants in and around Eocene Lakes of the Interior", in Ludvigson, Rolf (ed.), Life in Stone: a Natural History of British Columbia's Fossils, Vancouver: UBCPess, pp. page 234 following, ISBN 0774805781
{{citation}}:|pages=has extra text (help).
See also
External links
- Partial Prunus species listing: by National Genetics Resources Program