Oenothera is a genus of about 145 [3] species of herbaceous flowering plants native to the Americas. [4] It is the type genus of the family Onagraceae. Common names include evening primrose, suncups, and sundrops. They are not closely related to the true primroses (genus Primula ).
The species vary in size from small alpine plants 10 centimeters tall, such as O. acaulis from Chile, to vigorous lowland species growing to 3 meters, such as O. stubbei from Mexico. The leaves form a basal rosette at ground level and spiral up to the flowering stems. The blades are dentate or deeply lobed (pinnatifid). The flowers of many species open in the evening, hence the name "evening primrose". They may open in under a minute. Most species have yellow flowers, but some have white, purple, pink, or red. Most native desert species are white. Oenothera caespitosa , a species of western North America, produces white flowers that turn pink with age. [5] One of the most distinctive features of the flower is the stigma, which has four branches in an X shape. [6]
Oenothera flowers are pollinated by insects, such as moths and bees. Like many other members of the Onagraceae, however, the pollen grains are loosely held together by viscin threads, so only insects that are morphologically specialized to gather this pollen can effectively pollinate the flowers. Bees with typical scopa cannot hold it. Also, the flowers open at a time when most bee species are inactive, so the bees which visit Oenothera are generally vespertine temporal specialists: bees that forage in the evening. The seeds ripen from late summer to fall.
Oenothera are used as food plants by the larvae of some Lepidoptera species, including the large white-lined sphinx ( Hyles lineata ). [7] The flower moths Schinia felicitata and S. florida both feed exclusively on the genus, and the former is limited to O. deltoides.
In the wild, some species of evening primrose act as primary colonizers, quickly appearing in recently cleared areas. They germinate in disturbed soils, and can be found in habitat types such as dunes, roadsides, railway embankments, and waste areas. They are often casual and are eventually out competed by other species.
Based on observations of evening primroses ( O. drummondii ), a study discovered that within minutes of sensing the sound waves of nearby bee wings through flower petals, the concentration of the sugar in the plant's nectar was increased by an average of 20 percent. Experiments were also conducted on flowers with the petals removed. No change in nectar production was noted, indicating that it is indeed the flowers that have the job of the ears. [8]
The genus Oenothera may have originated in Mexico and Central America, [9] [10] and spread farther north in North America and into South America. With the advent of international travel, species are now found in most temperate regions of the world. In Europe alone there are about 70 introduced species of Oenothera. [4] During the Pleistocene era a succession of ice ages swept down across North America, with intervening warm periods. This occurred four times, and the genus experienced four separate waves of colonization, each hybridizing with the survivors of previous waves. [10] [11] This formed the present-day subsection Euoenothera. The group is genetically and morphologically diverse and the species are largely interfertile, so the species boundaries have been disputed amongst taxonomists. [9] [12]
The pattern of repeated colonizations resulted in a unique genetic conformation in the Euoenothera whereby the chromosomes at meiosis can form circles rather than pairs. This is the result of several reciprocal translocations between chromosomes such that the pairing occurs only at the tips. This phenomenon apparently has non-Mendelian genetic consequences; with this mode of chromosome segregation and a system of balanced-lethal genes, genetic recombination is prevented and the plants display the hybrid vigor of heterosis. [13] This resulted in the evolution of many sympatric races in North America east of the Rocky Mountains. Analysis of the cytology of these races and of artificial hybrids between them increased understanding of the genetic and geographic evolution of the Euoenothera. This subject was a major area of genetic research during the first half of the 20th century. [14] [15]
The appearance of sudden changes in Oenothera lamarckiana led the pioneering geneticist Hugo de Vries to propose what he called "mutation theory" in 1901 (Mutationstheorie in the German the original article was written in). [16] This asserted that speciation was driven by sudden large mutations able to produce new varieties in a single step. The understanding that the observed changes in hybrids of the plant were caused by chromosome duplications (polyploidy) rather than gene mutation did not come until much later. [17] [18]
Evening primroses were originally assigned to the genus Onagra, which gave the family Onagraceae its name. Onagra '[food of] onager' was first used in botany in 1587, and in English in Philip Miller's 1754 Gardeners Dictionary: Abridged. The modern name Oenothera was published by Carolus Linnaeus in his Systema Naturae . Its etymology is uncertain, but it is believed to be derived from the Greek words οίνος θήρα (oinos thera) 'wine seeker'. [19]
The genus is divided into 18 sections and additionally into several subsections and series. [1]
Certain Oenothera plants have edible parts. The roots of O. biennis are reportedly edible in young plants. So are the flowers which have a sweet, crunchy taste. [20]
The common evening primrose, O. biennis, is commonly sold as a dietary supplement in capsules containing the seed oil. [21] The main phytochemical in this evening primrose seed oil is gamma-linolenic acid. [21]
There is no high-quality scientific evidence that O. biennis or evening primrose oil has any effect on human diseases or promotion of health, [21] [22] and specifically no evidence that it is effective to treat atopic dermatitis or cancer. [21] [23] Research indicates that orally-administered evening primrose oil does not relieve symptoms of premenstrual syndrome, [24] [25] and does not have an effect on shortening the length of pregnancy or labor. [26] [27] [28] [29]
Consuming evening primrose oil may cause headache or stomach upset, may increase the risk of complications during pregnancy, and may increase the risk of bleeding in people given prescription drugs as anticoagulants, such as warfarin. [30]
A number of perennial members of the genus are commonly cultivated and used in landscaping in the southwestern United States. Popular species include tufted evening primrose ( Oenothera caespitosa ), Mexican evening primrose ( Oenothera berlanderii ), and Saltillo evening primrose ( Oenothera stubbei ). [31]
Annual evening primroses are also popular ornamental plants in gardens. Many are fairly drought-resistant.
The first plants to arrive in Europe reached Padua from Virginia in 1614 and were described by the English botanist John Goodyer in 1621. Some species are now also naturalized in parts of Europe and Asia, and can be grown as far north as 65°N in Finland. The UK National Council for the Conservation of Plants and Gardens, based at Wisley, maintains an Oenothera collection as part of its National Collections scheme.
The Onagraceae are a family of flowering plants known as the willowherb family or evening primrose family. They include about 650 species of herbs, shrubs, and trees in 17 genera. The family is widespread, occurring on every continent from boreal to tropical regions.
Oenothera biennis, the common evening-primrose, is a species of flowering plant in the family Onagraceae, native to eastern and central North America, from Newfoundland west to Alberta, southeast to Florida, and southwest to Texas, and widely naturalized elsewhere in temperate and subtropical regions. Evening primrose oil is produced from the plant.
Manduca quinquemaculata, the five-spotted hawkmoth, is a brown and gray hawk moth of the family Sphingidae. The caterpillar, often referred to as the tomato hornworm, can be a major pest in gardens; they get their name from a dark projection on their posterior end and their use of tomatoes as host plants. Tomato hornworms are closely related to the tobacco hornworm Manduca sexta. This confusion arises because caterpillars of both species have similar morphologies and feed on the foliage of various plants from the family Solanaceae, so either species can be found on tobacco or tomato leaves. Because of this, the plant on which the caterpillar is found does not indicate its species.
Gaura was a genus of flowering plants in the family Onagraceae, native to North America. The name was derived from Greek γαῦρος (gaûros) meaning "superb" and named in reference to the stature and floral display of some species in this genus. The genus included many species known commonly as beeblossoms. Genetic research showed that the genus was paraphyletic unless the monotypic genus Stenosiphon is included within Gaura, increasing the number of species in the genus to 22. Gaura is now a synonym of Oenothera, with the bulk of the Gaura taxa in genus Oenotherasect. Gaura(L.) W.L.Wagner &Hoch.
Oenothera fruticosa, the narrowleaf evening primrose or narrow-leaved sundrops, is a species of flowering plant in the evening primrose family.
Oenothera caespitosa, known commonly as tufted evening primrose, desert evening primrose, rock-rose evening primrose, or fragrant evening primrose, is a perennial plant of the genus Oenothera native to much of western and central North America, in habitats such as talus slopes and sandy plains. It is normally night-blooming.
Oenothera elata is a species of Oenothera known by the common name Hooker's evening primrose or tall evening primrose. Subspecies include hookeri, hirsutissima, longisima, jamesii, villosa and elata. It is native to much of western and central North America. The plants are quite tall, especially the hookeri subspecies, native to California, which can reach about 1.8 meters height. The plants are found along roadsides, in moist meadows, or in woodland, from sea level up to 9,000 ft (2,700 m) in elevation.
Oenothera deltoides subsp. howellii, the Antioch Dunes evening primrose, is an endangered subspecies of plant in the family Onagraceae, genus Oenothera, and species Oenothera deltoides.
Oenothera macrocarpa, the bigfruit evening primrose, Ozark sundrops, Missouri evening primrose, or Missouri primrose, is a species of flowering plant in the evening primrose family Onagraceae, native to northeast Mexico and the south-central United States, where it is found in calcareous prairies and limestone outcrops.
Oenothera harringtonii is a species of flowering plant in the evening primrose family known by the common names Arkansas Valley evening primrose and Colorado Springs evening primrose. It is endemic to the state of Colorado in the United States.
Oenothera gaura, formerly known as Gaura biennis, the biennial gaura or biennial beeblossom, is a North American flowering plant that can reach 6 ft (1.8 m) in height at maturity. Its upper half is made up of flowering stems, which are covered with soft, white hairs. It has light pink colored flowers, which turn a vibrant red/pink color in the late summer to early fall seasons. These colors make this plant attractive to butterflies and bees, and are in full bloom just before many fall plant species begin to bloom.
Plant bioacoustics refers to the creation of sound waves by plants. Measured sound emissions by plants as well as differential germination rates, growth rates and behavioral modifications in response to sound are well documented. Plants detect neighbors by means other than well-established communicative signals including volatile chemicals, light detection, direct contact and root signaling. Because sound waves travel efficiently through soil and can be produced with minimal energy expenditure, plants may use sound as a means for interpreting their environment and surroundings. Preliminary evidence supports that plants create sound in root tips when cell walls break. Because plant roots respond only to sound waves at frequencies which match waves emitted by the plants themselves, it is likely that plants can receive and transduce sound vibrations into signals to elicit behavioral modifications as a form of below ground communication.
Oenothera heterophylla, commonly called variable evening-primrose, is a species of flowering plant in the evening-primrose family (Onagraceae). It is native to the South Central region of the United States, with a disjunct eastern population in Alabama. It has been recorded as an introduced waif in Missouri.
Oenothera parviflora, the northern evening primrose, is a species of flowering plant in the family Onagraceae. It is native to northeastern North America, and invasive in Europe, Asia, South Africa and New Zealand.
Robert A. Raguso is an American biologist and professor at Cornell University in the Department of Neurobiology and Behavior. He has expanded the field of chemical ecology by introducing and pioneering floral scent as a key component of plant-pollinator communication, with special focus on hawkmoths and Clarkia plants.
Oenothera versicolor, the red evening-primrose, is a species of flowering plant in the family Onagraceae, native to South America, from Peru and Ecuador down to Bolivia and Northern Argentina This species is not as common in cultivation as other members of the genus but popular cultivars including 'Sunset Boulevard' are grown in gardens around the temperate world as the plant is hardy down to at least −10 °C (14 °F).
Oenothera tetragona, the glaucous evening primrose, is a species of flowering plant in the family Onagraceae, native to eastern North America, and introduced to Germany, the Czech Republic, and Myanmar. The Royal Horticultural Society considers it a good plant to attract pollinators. There is a cultivar, 'Glaber', also known as 'Clarence Elliott'.
Oenothera stricta, the fragrant evening primrose, is a species of flowering plant in the family Onagraceae. It is native to the Desventurados Islands, Chile, and southern Argentina, and it has been introduced to many locations around the world. The unimproved species is available from commercial suppliers, as is a cultivar, 'Sulphurea'. The Royal Horticultural Society considers both to be good plants to attract pollinators.
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