Prunus
Prunus is a genus of flowering trees and shrubs from the family Rosaceae. The genus includes plums, cherries, peaches, nectarines, apricots and almonds. The genus has a cosmopolitan distribution, being native to the temperate regions of North America, the neotropics of South America, and temperate and tropical regions of Eurasia and Africa, There are about 340 accepted species as of 2024.
Many members of the genus are widely cultivated for their sweet, fleshy fruit and for decorative purposes of their flowers. Prunus fruit are drupes, or stone fruits. The fleshy mesocarp surrounding the endocarp is edible while the endocarp itself forms a hard, inedible shell called the pyrena. This shell encloses the seed, which is edible in some species, but poisonous in many others. Besides being eaten off the hand, most Prunus fruit are also commonly used in processing, such as jam production, canning, drying, and the seeds for roasting.
Description
Members of the genus are either deciduous or evergreen. A few species have spiny stems. The leaves are simple, alternate, usually lanceolate, unlobed, and often with nectaries on the leaf stalk along with stipules. The flowers are usually white to pink, sometimes red, with five petals and five sepals. Numerous stamens are present. Flowers are borne singly, or in umbels of two to six or sometimes more on racemes. The fruit is a fleshy drupe with a single relatively large, hard-coated seed.Taxonomy
Within the rose family Rosaceae, it was traditionally placed as a subfamily, the Amygdaloideae, but was sometimes placed in its own family, the Prunaceae. More recently, Prunus is thought to have evolved from within a much larger clade now called subfamily Amygdaloideae.Classification
Evolutionary history
The oldest fossils confirmed to belong to Prunus date to the Eocene, and are found across the Northern Hemisphere. Older potential Late Cretaceous records are unconfirmed.The earliest known fossil Prunus specimens are wood, drupe, seed, and a leaf from the middle Eocene of the Princeton Chert of British Columbia, Canada. Using the known age as calibration data, a partial phylogeny of some of the Rosaceae from a number of nucleotide sequences was reconstructed. Prunus and its sister clade Maloideae has been suggested to have diverged which is within the Lutetian, or older middle Eocene. Stockey and Wehr report: "The Eocene was a time of rapid evolution and diversification in Angiosperm families such as the Rosaceae...." The oldest fossil species is Prunus cathybrownae from the Klondike Mountain Formation.
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: the McAbee Fossil Beds, British Columbia; the Klondike Mountain Formation around Republic, Washington, and the Allenby Formation around Princeton, British Columbia, while Prunus is found at those locations plus the Coldwater Beds of Quilchena, British Columbia and Chu Chua Formation around Chu Chua, British Columbia. A review of research on the Eocene Okanagan Highlands reported that the Rosaceae were more diverse at higher altitudes. The Okanagan highlands formations date to as early as 52 mya, but the 44.3 mya date might still apply. The authors state that "the McAbee flora records a diverse early middle Eocene angiosperm-dominated forest."
Linnean classification
In 1737, Carl Linnaeus used four genera to include the species of modern Prunus—''Amygdalus, Cerasus, Prunus, and Padus—but simplified it to Amygdalus and Prunus'' in 1758. Since then, the various genera of Linnaeus and others have become subgenera and sections, as all the species clearly are more closely related. Liberty Hyde Bailey said: "The numerous forms grade into each other so imperceptibly and inextricably that the genus cannot be readily broken up into species."Traditional classification
Historical treatments break the genus into several different genera, but this segregation is not currently widely recognised other than at the subgeneric rank. The ITIS recognises just the single genus Prunus, with an open list of species, all of which are given at List of Prunus species.One treatment of the subgenera derives from the work of Alfred Rehder in 1940. Rehder hypothesized five subgenera: Amygdalus, Prunus, Cerasus, Padus, and Laurocerasus. To them C. Ingram added Lithocerasus. The six subgenera are described as follows:
- Subgenus Amygdalus, almonds and peaches: axillary buds in threes ; 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 amygdalus
- 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
- Subgenus Cerasus, true 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
- Subgenus Lithocerasus, bush 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
- 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, now known to be polyphyletic
- Subgenus Laurocerasus, cherry laurels: evergreen ; axillary buds single; flowers in early spring in racemes, not on leafed shoots, short-stalked; fruit not grooved, stone smooth; type species: ''Prunus laurocerasus''
Phylogenetic classification
An extensive phylogenetic study based on different chloroplast and nuclear sequences divides Prunus into three subgenera:- Subg. Padus: In addition to species of Padus, this subgenus also includes species of Maddenia, Laurocerasus and Pygeum.
- Subg. Cerasus: This subgenus includes true cherries such as sweet cherry, sour cherry, mahaleb cherry and flowering cherry">flowering plant">flowering cherry.
- Subg. Prunus: This subgenus includes the following sections:
- * Sect. Prunus: Old World plums
- * Sect. Prunocerasus: New World plums
- * Sect. Armeniaca: apricots
- * Sect. Microcerasus: bush cherries
- * Sect. Amygdalus: almonds
- * Sect. Persica: peaches
- * Sect. Emplectocladus: desert almonds
Species
The lists below are incomplete, but include most more commonly cultivated species.Afro-Eurasian species
P. africana – African cherryP. amygdalus – almondP. apetala – clove cherryP. armeniaca – apricotP. avium – sweet cherry or wild cherryP. brigantina – Briançon apricotP. buergeriana – dog cherryP. campanulata – Taiwan cherryP. canescens – gray-leaf cherryP. cerasifera – cherry plumP. cerasoides – wild Himalayan cherryP. cerasus – sour cherryP. ceylanica – Ceylon cherry P. cocomilia – Italian plumP. cornuta – Himalayan bird cherryP. davidiana – David's peachP. darvasica – Darvaz plumP. domestica – common plumP. fruticosa – European dwarf cherryP. glandulosa – Chinese bush cherryP. grayana – Japanese bird cherryP. incana – willow-leaf cherryP. incisa – Fuji cherryP. jacquemontii – Afghan bush cherryP. japonica – Japanese bush cherryP. laurocerasus – cherry laurelP. lusitanica – Portugal laurelP. maackii – Manchurian cherryP. mahaleb – Mahaleb cherryP. mandshurica – Manchurian apricotP. maximowiczii – Korean cherryP. mume – Chinese plumP. nipponica – Japanese alpine cherryP. padus – bird cherryP. persica – peachP. pseudocerasus – Chinese sour cherryP. prostrata – mountain cherryP. salicina – Japanese plumP. sargentii – north Japanese hill cherryP. scoparia – mountain almondP. serrula – Tibetan cherryP. serrulata – Japanese cherryP. sibirica – Siberian apricotP. simonii – apricot plumP. speciosa – Oshima cherryP. spinosa – blackthorn, sloeP. ssiori – Hokkaido bird cherryP. subhirtella – winter-flowering cherryP. tenella – dwarf Russian almondP. tomentosa – Nanking cherryP. triloba – flowering plumP. turneriana – almondbarkP. ursina – Bear's plum- P. × yedoensis – Yoshino cherryP. zippeliana – big-leaf cherry
Species found in the Americas
P. alabamensis – Alabama cherryP. alleghaniensis – Allegheny plumP. americana – American plumP. andersonii – desert peachP. angustifolia – Chickasaw plumP. brasiliensis – Brazilian cherryP. buxifolia – chuwacá P. caroliniana – Carolina laurelcherryP. cortapicoP. emarginata – bitter cherryP. eremophila – Mojave Desert plumP. fasciculata – wild almondP. fremontii – desert apricotP. geniculata – scrub plumP. gentryi – Gentry cherryP. gracilis – Oklahoma plumP. havardii – Havard's plumP. hortulana – Hortulan plumP. huantensisP. ilicifolia – hollyleaf cherryP. integrifoliaP. maritima – beach plumP. mexicana – Mexican plumP. minutiflora – Texas almondP. murrayana – Murray's plumP. myrtifolia – West Indies cherryP. nigra – Canada plumP. occidentalis – western cherry laurelP. pensylvanica – pin cherryP. pleuradenia – Antilles cherryP. pumila – sand cherryP. rigidaP. rivularis – creek plumP. serotina – black cherryP. subcordata – Klamath plumP. subcorymbosaP. texana – peachbushP. umbellata – flatwoods plumP. virginiana – chokecherryEtymology
The Online Etymology Dictionary presents the customary derivations of plum and prune from Latin prūnum, the plum fruit. The tree is prūnus; and Pliny uses prūnus silvestris to mean the blackthorn. The word is not native Latin, but is a loan from Greek προῦνον, which is a variant of προῦμνον, origin unknown. The tree is προύμνη. Most dictionaries follow Hoffman, Etymologisches Wörterbuch des Griechischen, in making some form of the word a loan from a pre-Greek language of Asia Minor, related to Phrygian.The first use of Prunus as a genus name was by Carl Linnaeus in Hortus Cliffortianus of 1737, which went on to become Species Plantarum.
Pests and diseases
Various Prunus species are winter hosts of the Damson-hop aphid, Phorodon humuli, which is destructive to hops Humulus lupulus just at the time of their maturity, so plum trees should not be grown in the vicinity of hop fields.Corking is the drying or withering of fruit tissue. In stone fruit, it is often caused by a lack of boron and/or calcium.
Gummosis is a nonspecific condition of stone fruits in which gum is exuded and deposited on the bark of trees. Gum is produced in response to any type of wound – insect, mechanical injury, or disease.
Apiosporina morbosa is a major fungal disease in the Northern Americas, with many urban centres running black knot fungus management programs. This disease is best managed by physical removal of knot-bearing branches to prevent spore spread and immediate disposal of infected tissue. Chemical treatment is not largely effective, as trees can easily be re-infected by neighbouring knots.
Laetiporus gilbertsoni, is a serious cubic brown rot parasite which attacks certain species of decorative red-leaf plum trees in the genus Prunus on the Pacific coast of North America.
Cultivation
[Image:Nectarine Fruit Development.jpg|thumb|The development sequence of a nectarine (P. persica) over a 7.5-month period, from bud formation in early winter to fruit ripening in midsummer]The genus Prunus includes the almond, the nectarine and peach, several species of apricots, cherries, and plums, all of which have cultivars developed for commercial fruit and nut production. The almond is not a true nut; the edible part is the seed. Other species are occasionally cultivated or used for their seed and fruit.
A number of species, hybrids, and cultivars are grown as ornamental plants, usually for their profusion of flowers, sometimes for ornamental foliage and shape, and occasionally for their bark.
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, some becoming naturalised.
The Tree of 40 Fruit has 40 varieties grafted on to one rootstock.
Species such as blackthorn, are grown for hedging, game cover, and other utilitarian purposes.
The wood of some species is prized as a furniture and cabinetry timber, especially in North America.
Many species produce an aromatic gum from wounds in the trunk; this is sometimes used medicinally. Other minor uses include dye production.
Pygeum, a herbal remedy containing extracts from the bark of Prunus africana, is used as to alleviate some of the discomfort caused by inflammation in patients with benign prostatic hyperplasia.
Prunus species are food plants for the larvae of many Lepidoptera species.
Prunus species are included in the Tasmanian Fire Service's list of low flammability plants, indicating that it is suitable for growing within a building protection zone.
Ornamental ''Prunus''
Ornamentals include the group that may be collectively called "flowering cherries".Toxicity
Many species are cyanogenic; that is, they contain compounds called cyanogenic glucosides, notably amygdalin, which, on hydrolysis, yield hydrogen cyanide. Although the fruits of some may be edible by humans and livestock, seeds, leaves and other parts may be toxic, some highly so. The plants contain no more than trace amounts of hydrogen cyanide, but on decomposition after crushing and exposure to air or on digestion, poisonous amounts may be generated. The trace amounts may give a characteristic taste with increasing bitterness in larger quantities, less tolerable to people than to birds, which habitually feed on specific fruits.Benefits to human health
People are often encouraged to consume many fruits because they are rich in a variety of nutrients and phytochemicals that are supposedly beneficial to human health. The fruits of Prunus often contain many phytochemicals and antioxidants. These compounds have properties that have been linked to preventing different diseases and disorders. Research suggests that the consumption of these fruits reduces the risk of developing diseases such as cardiovascular diseases, cancer, diabetes, and other age-related declines. Many factors can affect the levels of bioactive compounds in the different fruits of the genus Prunus, including the environment, season, processing methods, orchard operations, and postharvest management.Cherries
Cherries contain many different phenolic compounds and anthocyanins, which are indicators of being rich in antioxidants. Recent research has linked the phenolic compounds of the sweet cherry with antitumor properties.Reactive oxygen species include superoxide radicals, hydrogen peroxide, hydroxyl radicals, and singlet oxygen; they are the byproducts of metabolism. High levels of ROS lead to oxidative stress, which causes damage to lipids, proteins, and nucleic acids. The oxidative damage results in cell death, which ultimately leads to numerous diseases and disorders. Antioxidants act as a defense mechanism against the oxidative stress. They are used to remove the free radicals in a living system that are generated as ROS. Some of those antioxidants include glutathione S-transferase, glutathione peroxidase, superoxide dismutase, and catalase. The antioxidants present in cherry extracts act as inhibitors of the free radicals. However, the DNA and proteins can be damaged when an imbalance occurs in the level of free radicals and the antioxidants. When not enough antioxidants are available to remove the free radicals, many diseases can occur, such as cancers, cardiovascular diseases, Parkinson's disease, etc. Recent studies have shown that using natural antioxidants as a supplement in chemotherapy can decrease the amount of oxidative damage. Some of these natural antioxidants include vitamin C, tocopherol, and epigallocatechin gallate; they can be found in certain cherry extracts.