Passion flowers produce regular and usually showy flowers with a distinctive corona. There can be as many as eight concentric coronal series, as in the case of P. xiikzodz.[3] The flower is pentamerous (except for a few Southeast Asian species) and ripens into an indehiscent fruit with numerous seeds.
The fruit ranges from 5–20 centimetres (2–8 in) long and 2.5–5 cm (1–2 in) across, depending upon the species or cultivar.
Passiflora is the most species rich genus of both the family Passifloraceae and the tribe Passifloreae. With over 550 species, an extensive hierarchy of infrageneric ranks is required to represent the relationships of the species. The infrageneric classification of Passiflora not only uses the widely used ranks of subgenus, section and series, but also the rank of supersection.
The New World species of Passiflora were first divided among 22 subgenera by Killip (1938) in the first monograph of the genus.[8] More recent work has reduced these to 4, which are commonly accepted today (in order from most basally to most recently branching):[9]
Astrophea (Americas, ~60 species), trees and shrubs with simple, unlobed leaves
Passiflora (Americas, ~250 species), woody vines with large flowers and elaborate corolla
Deidamioides (Americas, 13 species), woody or herbaceous vines
Decaloba (Americas, Asia and Australasia, ~230 species), herbaceous vines with palmately veined leaves
Some studies have shown that the segregate Old World genera Hollrungia and Tetrapathaea are nested within Passiflora, and form a fifth subgenus (Tetrapathaea).[10] Other studies support the current four subgenus classification.[11]
Relationships below the subgenus level are not known with certainty and are an active area of research. The Old World species form two clades – supersection Disemma (part of subgenus Decaloba) and subgenus Tetrapathaea. The former is composed of 21 species divided into sections Disemma (three Australian species), Holrungiella (one New Guinean species) and Octandranthus (seventeen south and east Asian species).[12]
The remaining (New World) species of subgenus Decaloba are divided into seven supersections. Supersection Pterosperma includes four species from Central America and southern Mexico. Supersection Hahniopathanthus includes five species from Central America, Mexico and northernmost South America. Supersection Cicea includes nineteen species, with apetalous flowers. Supersection Bryonioides includes twenty-one species, with a distribution centered on Mexico. Supersection Auriculata includes eight species from South America, one of which is also found in Central America. Supersection Multiflora includes nineteen species. Supersection Decaloba includes 123 species.[13]
Distribution
Passiflora has a largely neotropic distribution, unlike other genera in the family Passifloraceae, which includes more Old World species (such as the genus Adenia). The vast majority of Passiflora are found in Mexico, Central America, the United States and South America, although there are additional representatives in Southeast Asia and Oceania.[14] New species continue to be identified: for example, P. xishuangbannaensis and P. pardifolia have only been known to the scientific community since 2005 and 2006, respectively.
Some species of Passiflora have been naturalized beyond their native ranges. For example, the blue passion flower (P. caerulea) now grows wild in Spain.[15] The purple passionfruit (P. edulis) and its yellow relative flavicarpa have been introduced in many tropical regions as commercial crops.
Passion flowers have floral structures adapted for biotic pollination. Pollinators of Passiflora include bumblebees, carpenter bees (e.g., Xylocopa sonorina), wasps, bats, and hummingbirds (especially hermits such as Phaethornis); some others are additionally capable of self-pollination. Passiflora often exhibit high levels of pollinator specificity, which has led to frequent coevolution across the genus. The sword-billed hummingbird (Ensifera ensifera) is a notable example: it, with its immensely elongated bill, is the sole pollinator of 37 species of high AndeanPassiflora in the supersection Tacsonia.[16]
The leaves are used for feeding by the larvae of a number of species of Lepidoptera. Famously, they are exclusively targeted by many butterfly species of the tribe Heliconiini. The many defensive adaptations visible on Passiflora include diverse leaf shapes (which help disguise their identity), colored nubs (which mimic butterfly eggs and can deter Heliconians from ovipositing on a seemingly crowded leaf), extrafloral nectaries, trichomes, variegation, and chemical defenses.[17] These, combined with adaptations on the part of the butterflies, were important in the foundation of coevolutionary theory.[18][19]
Recent studies have shown that passiflora both grow faster and protect themselves better in high-nitrogen soils. In low-nitrogen environments, passiflora focus on growth rather than defense and are more vulnerable to herbivores.[20]
The following lepidoptera larvae are known to feed on Passiflora:
Cydno longwing (Heliconius cydno), one of few Heliconians to feed on multiple species of Passiflora[21]
Gulf fritillary (Agraulis vanillae), which feeds on several species of Passiflora, such as Passiflora lutea, Passiflora affinis,[22][23] stinking passion flower (P. foetida),[24] and Maypop (P. incarnata)
The generally high pollinator and parasite specificity in Passiflora may have led to the tremendous morphological variation in the genus. It is thought to have among the highest foliar diversity among all plant genera,[8] with leaf shapes ranging from unlobed to five-lobed frequently found on the same plant.[26]Coevolution can be a major driver of speciation, and may be responsible for the radiation of certain clades of Passiflora such as Tacsonia.
Banana passion flower or "banana poka" (P. tarminiana), originally from Central Brazil, is an invasiveweed, especially on the islands of Hawaii. It is commonly spread by feralpigs eating the fruits. It overgrows and smothers stands of endemic vegetation, mainly on roadsides. Blue passion flower (P. caerulea) is an invasive species in Spain and considered likely to threaten ecosystems there.[15]
On the other hand, some species are endangered due to unsustainable logging and other forms of habitat destruction. For example, the Chilean passion flower (P. pinnatistipula) is a rare vine growing in the Tropical Andes southwards from Venezuela between 2,500 and 3,800 metres (8,200 and 12,500 ft) in altitude, and in Coastal Central Chile, where it only occurs in a few tens of square kilometres of fog forest by the sea, near Zapallar. P. pinnatistipula has a round fruit, unusual in Tacsonia group species like banana passion flower and P. mixta, with their elongated tubes and brightly red to rose-colored petals.[citation needed]
Passion flower is not recommended during pregnancy because it may induce contractions.[28][4] Consuming passion flower products may cause drowsiness, nausea, dizziness, abnormal heart rhythms, asthma, or rhinitis.[28][4]
A number of species of Passiflora are cultivated outside their natural range for both their flowers and fruit. Hundreds of hybrids have been named; hybridizing is currently being done extensively for flowers, foliage and fruit. The following hybrids and cultivars have gained the Royal Horticultural Society's Award of Garden Merit:
During the Victorian era the flower (which in all but a few species lasts only one day) was very popular, and many hybrids were created using the winged-stem passion flower (P. alata), the blue passion flower (P. caerulea) and other tropical species.
Many cool-growing Passiflora from the Andes Mountains can be grown successfully for their beautiful flowers and fruit in cooler Mediterranean climates, such as the Monterey Bay and San Francisco in California and along the western coast of the U.S. into Canada. One blue passion flower or hybrid even grew to large size at Malmö Central Station in Sweden.[32]
Most species have round or elongated edible fruit.
The passion fruit or maracujá (P. edulis) is cultivated extensively in the Caribbean, South America, south Florida and South Africa for its fruit, which is used as a source of juice. A small pink fruit that wrinkles easily and a larger shiny yellow to orange fruit are traded under this name. The latter is usually considered just a variety of flavicarpa, but seems to be more distinct.[citation needed]
Sweet granadilla (P. ligularis) is another widely grown species. In large parts of Africa it is the plant called "passionfruit": confusingly, in South African English the latter species is more often called granadilla (without an adjective). Its fruit is somewhat intermediate between the two sold as P. edulis.
Maypop (P. incarnata), a common species in the southeastern US. This is a subtropical representative of this mostly tropical family. However, unlike the more tropical cousins, this particular species is hardy enough to withstand the cold down to −20 °C (−4 °F) before its roots die (it is native as far north as Pennsylvania and has been cultivated as far north as Boston and Chicago.) The fruit is sweet, yellowish, and roughly the size of a chicken's egg; it enjoys some popularity as a native plant with edible fruit and few pests.
The blue passionflower (Passiflora caerulea) produces bright orange fruit with numerous seeds. While the fruit is edible, it is often described as being bland in comparison to other edible passionfruit, or with a flavour vaguely similar to blackberries.[35]
A native source of beta-Carbolines (e.g., passion flower in North America) is mixed with Desmanthus illinoensis (Illinois bundleflower) root bark to produce a hallucinogenic drink called prairiehuasca, which is an analog of the shamanic brew ayahuasca.[38]
Blue passion flower (P. caerulea) showing most elements of the Christian symbolismPassiflora 'Soi Fah', a.k.a. Krishnakamala in India
The passion in passion flower purportedly refers to the passion of Jesus in Christian theology;[40] the word passion comes from the Latinpassio, meaning 'suffering'. In the 15th and 16th centuries, Spanish Christian missionaries adopted the unique physical structures of this plant, particularly the numbers of its various flower parts, as symbols of the last days of Jesus and especially his crucifixion:[41]
The pointed tips of the leaves were taken to represent the Holy Lance.
The three stigmas represent three nails and the five anthers below them five hammers or five wounds (four by the nails and one by the lance).
The blue and white colors of many species' flowers represent Heaven and Purity.
In addition, the flower is open for three days, symbolising the three years of Jesus' ministry.[42]
The flower has been given names related to this symbolism throughout Europe since the 15th century. In Spain, it is known as espina de Cristo ('thorn of Christ'). Older Germanic names[43] include Christus-Krone ('Christ's crown'), Christus-Strauss ('Christ's bouquet'),[44]Dorn-Krone ('crown of thorns'), Jesus-Lijden ('Jesus' passion'), Marter ('passion')[45] or Muttergottes-Stern ('Mother of God's star').[46]
Outside the Roman Catholic heartland, the regularly shaped flowers have reminded people of the face of a clock. In Israel they are known as "clock-flower" (שעונית) and in Greece as "clock plant" (ρολογιά); in Japan too, they are known as tokeisō (時計草, 'clock plant'). In Hawaiian, they are called lilikoʻi;[47]lī is a string used for tying fabric together, such as a shoelace, and liko means 'to spring forth leave'.[48]
In India, it is known as Krishnakamala because of its dark violet blue colour which resembles Bhagwan Krishna.
Gallery
Bud of the passion flower
Passiflora 'Incense', a hybrid of the Brazilian species P. cincinnata and the American species P. incarnata
^ abKillip, E.P. (1938). The American Species of Passifloraceae. Chicago, US: Field Museum of Natural History.
^Feuillet, C.; MacDougal, J. (2004). "A new infrageneric classification of Passiflora L. (Passifloraceae)". Passiflora. 13 (2): 34–35, 37–38.
^Krosnick, S.E.; Ford, A.J.; Freudenstein, J.V. (2009). "Taxonomic Revision of Passiflora Subgenus Tetrapathea Including the Monotypic Genera Hollrungia and Tetrapathea (Passifloraceae), and a New Species of Passiflora". Systematic Botany. 34 (2): 375–385. doi:10.1600/036364409788606343. S2CID86038282.
^Hansen, K.A.; Gilbert, L.E.; Simpson, B.B.; Downie, S.R.; Cervi, A.C.; Jansen, R.K. (2006). "Phylogenetic Relationships and Chromosome Number Evolution in Passiflora". Systematic Botany. 31 (1): 138–150. doi:10.1600/036364406775971769. S2CID4820527.
^de Castro, É.C.P.; Zagrobelny, M.; Cardoso, M.Z.; Bak, S. (2017). "The arms race between heliconiine butterflies and Passiflora plants - new insights on an ancient subject". Biological Reviews. 93 (1): 555–573. doi:10.1111/brv.12357. PMID28901723. S2CID23953807.
^Ehrlich, P.R.; Raven, P.H. (1964). "Butterflies and Plants: A Study in Coevolution". Evolution. 18 (4): 586–608. doi:10.2307/2406212. JSTOR2406212.
^ abcdef"Passionflower". National Center for Complementary and Integrative Health, US National Institutes of Health. 1 September 2016. Retrieved 30 October 2019.
^The University of Georgia - Center for Invasive Species and Ecosystem Health and the National Park Service (17 February 2011). "Invasive Plant Atlas of the United States". Retrieved 8 March 2011.
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