Passiflora


Passiflora, known also as the passion flowers or passion vines, is a genus of about 550 species of flowering plants, and the type genus of the family Passifloraceae.
Passiflora species are widely cultivated for their striking flowers, flavorful fruits, traditional medicinal uses, and roles in dietary supplements and ayahuasca analogs, with several ornamental hybrids earning Royal Horticultural Society awards.

Description

The genus mostly produces tendril-bearing vines, as well as some shrubs and trees. The plants can be woody or herbaceous.
The flowers are regular and usually showy, with a distinctive corona. There can be as many as eight concentric coronal series, as in the case of P. xiikzodz. and P. alata. The hallmark of the genus is the androgynophore, a central column to which the stamens and pistil are attached, which can be very long in some species such as P. coactilis. The flower is pentamerous and ripens into an indehiscent fruit with numerous seeds.
The fruit ranges from long and across, depending upon the species or cultivar.

Chemistry

Many Passiflora species have been found to contain beta-carboline harmala alkaloids, some of which are MAO inhibitors. The flower and fruit have only traces of these chemicals, but the leaves and the roots often contain more. The most common of these alkaloids is harman, but harmaline, harmalol, harmine, and harmol are also present. The species known to bear such alkaloids include: P. actinia, P. alata, P. alba, P. bryonioides, P. caerulea, P. capsularis, P. decaisneana, P. edulis, P. eichleriana, P. foetida, P. incarnata, P. quadrangularis, P. suberosa, P. subpeltata and P. warmingii.
Other compounds found in passion flowers are coumarins, maltol, phytosterols and cyanogenic glycosides which render some species, i.e. P. adenopoda, somewhat poisonous. Many flavonoids and their glycosides have been found in Passiflora, including apigenin, benzoflavone, homoorientin,, isoshaftoside, isovitexin, kaempferol, lucenin, luteolin,, passiflorine, quercetin, rutin, saponarin, shaftoside, vicenin and vitexin. Maypop, blue passion flower, and perhaps others contain the flavone chrysin. Also documented to occur at least in some Passiflora in quantity are the hydrocarbon nonacosane and the anthocyanidin pelargonidin-3-diglycoside.
The genus is rich in organic acids including formic, butyric, linoleic, linolenic, malic, myristic, oleic and palmitic acids as well as phenolic compounds, and the amino acid. Esters like ethyl butyrate, ethyl caproate, n-hexyl butyrate and n-hexyl caproate give the fruits their flavor and appetizing smell. Sugars, contained mainly in the fruit, are most significantly, and raffinose. Among enzymes, Passiflora was found to be rich in catalase, pectin methylesterase and phenolase.

Taxonomy

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 in the first monograph of the genus. More recent work has reduced these to 4, which are commonly accepted today :
  • Astrophea, trees and shrubs with simple, unlobed leaves
  • Passiflora, woody vines with large flowers and elaborate corolla
  • Deidamioides, woody or herbaceous vines
  • Decaloba, 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. Other studies support the current four subgenus classification.
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 and subgenus Tetrapathaea. The former is composed of 21 species divided into sections Disemma, Holrungiella and Octandranthus.
The remaining 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.

Distribution

Passiflora has a largely neotropic distribution, unlike other genera in the family Passifloraceae, which includes more Old World species. The vast majority of Passiflora are found in the United States and Latin America, although there are additional representatives in Southeast Asia and Oceania. 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 now grows wild in Spain. The purple passionfruit and its yellow relative flavicarpa have been introduced in many tropical regions as commercial crops.

Ecology

Passion flowers have floral structures adapted for biotic pollination. Pollinators of Passiflora include bumblebees, carpenter bees, wasps, bats, and hummingbirds ; 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 is a notable example: it, with its immensely elongated bill, is the sole pollinator of 37 species of high Andean Passiflora in the supersection Tacsonia.
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, colored nubs, extrafloral nectaries, trichomes, variegation, and chemical defenses. These, combined with adaptations on the part of the butterflies, were important in the foundation of coevolutionary theory.
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.
The following lepidoptera larvae are known to feed on Passiflora:
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, with leaf shapes ranging from unlobed to five-lobed frequently found on the same plant. Coevolution can be a major driver of speciation, and may be responsible for the radiation of certain clades of Passiflora such as Tacsonia.
The bracts of the stinking passion flower are covered by hairs which exude a sticky fluid. Many small insects get stuck to this and get digested to nutrient-rich goo by proteases and acid phosphatases. Since the insects usually killed are rarely major pests, this passion flower seems to be a protocarnivorous plant.
Banana passion flower or "banana poka", originally from Central Brazil, is an invasive weed, especially on the islands of Hawaii. It is commonly spread by feral pigs eating the fruits. It overgrows and smothers stands of endemic vegetation, mainly on roadsides. Blue passion flower is an invasive species in Spain and considered likely to threaten ecosystems there.
On the other hand, some species are endangered due to unsustainable logging and other forms of habitat destruction. For example, the Chilean passion flower is a rare vine growing in the Tropical Andes southwards from Venezuela between 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.
Notable and sometimes economically significant pathogens of Passiflora are several sac fungi of the genus Septoria, the undescribed proteobacterium called "Pseudomonas tomato", the Potyvirus ''passionfruit woodiness virus, and the Carlavirus Passiflora latent virus''.