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Published In: Species Plantarum 1: 346. 1753. (1 May 1753) (Sp. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library

Project Name Data (Last Modified On 6/2/2011)
Acceptance : Accepted
Project Data     (Last Modified On 6/3/2011)
Contributor Text: Peter C. Hoch and Peter H. Raven
Synonym Text: Onagra P. Miller, Gard. Dict. Abr, ed. 4: 1754; Spach, Nouv. Ann. Mus. Paris III. 4: 351. 1835; Shteinberg in Schischkin & Bobrov, Fl. URSS. 15: 628. 1949; Hartmannia Spach, Hist. VJg. Phan. 4: 378. 1835.
General/Distribution: A genus of about 125 species native to North and South America, with some species widely introduced as escapes from cultivation throughout the world. Several species are now extensively naturalized throughout many temperate regions of the world. Although the group is native only in the New World, several genetically distinctive strains have originated and subsequently become established in the Old World, following hybridization between introduced species. Many species of Oenothera, nearly all of which are weedy, are complex heterozygotes and form a ring of 14 or other large rings of chromosomes at meiotic metaphase I. Most complex heterozygotes have originated within the limits of a taxonomic species, while others have originated after hybridization between species. Genetic recombination is strongly restricted in these species on account of lethal genes or selective fertilization, predominant self-pollination, metacentric chromosomes which are involved in reciprocal translocations, and alternate disjunction at meiotic anaphase I. The two sets of 7 chromosomes behave then as if they are only a single set of chromosomes when segregating at anaphase. Therefore, any new hybridization event can, in effect, lead directly to the formation of a new 'species', whose progeny will breed true. This situation is not comparable with species recognized in most other groups of flowering plants. Represented in Pakistan by 4 naturalized or cultivated species.


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Annual, biennial, or perennial herbs, caulescent or acaulescent, with a taproot or spreading underground parts. Basal rosette present or absent; leaves alternate, stipules absent. Flowers 4-merous, actinomorphic, in axils of upper leaves, opening near sunset or near sunrise; floral tube well-developed and prolonged beyond the ovary, deciduous after anthesis. Petals yellow, purplish, or white; stamens 8, anthers versatile, the sporogenous tissue in each locale undivided; pollen shed singly; stigma deeply 4-lobed. Capsule many-seeded, sessile or pedicellate, mostly straight, terete or somewhat 4-angled, loculicidally dehiscent or indehiscent. Seeds naked, in 1 to several rows in each of the 4 locules. Basic chromosome number, x = 7.

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1 Petals yellow, 15-50 mm long; capsule sessile, not tapering to a stipe-like sterile portion. (2)
+ Petals rose to rose-purple, 4-12 mm long; capsule tapering to a stipe-like sterile portion. 4 Oenothera rosea
2 (1) Floral tube 2-5 cm long. Plants forming a rosett (3)
+ Floral tube 8-13 cm long. Plants not forming a rosette. 2 Oenothera affinis
3 (2) Capsule not enlarged distally. Stem pubescence with reddish-purple pustulate bases on at least some of the hairs. Seeds sharply angled, not beaked. 1 Oenothera glazioviana
+ Capsule conspicuously enlarged distally. Stem pubescence without reddish-purple pustulate bases. Seed elliptical, beaked. 3 Oenothera stricta Ledeb. ex Link subsp. stricta
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