Asimina triloba
From Wikipedia, the free encyclopedia
(Redirected from American Pawpaw)
This article is about the common pawpaw of eastern North America. For the unrelated tropical papaya fruit often called 'papaw' or 'pawpaw', see Carica papaya. For other uses, see Paw Paw (disambiguation).
 | This article needs additional citations for verification. (July 2012) |
| Asimina triloba | |
|---|---|
| Asimina triloba in fruit | |
| Scientific classification | |
| Kingdom: | Plantae |
| (unranked): | Angiosperms |
| (unranked): | Magnoliids |
| Order: | Magnoliales |
| Family: | Annonaceae |
| Genus: | Asimina |
| Species: | A. triloba |
| Binomial name | |
| Asimina triloba (L.) Dunal | |
 | |
| Range of A. triloba in the United States | |
Asimina triloba, the pawpaw, paw paw, paw-paw, or common pawpaw, is a species of Asimina (the pawpaw genus) in the same plant family (theAnnonaceae) as the custard-apple, cherimoya, sweetsop, ylang-ylang and soursop. The pawpaw is native to the Eastern, Southern, and MidwesternUnited States and adjacent southernmost Ontario, Canada, from New York west to southeastern Nebraska, and south to northern Florida and easternTexas.[1][2] The pawpaw is a patch-forming (clonal) understory tree found in well-drained, deep, fertile bottom-land and hilly upland habitat, with large, simple leaves and large fruits. The paw paw is the largest edible fruit indigenous to the United States.[2]
Names
This plant's scientific name is Asimina triloba. The genus name Asimina is adapted from the Native American name assimin[3] through the French colonial asiminier.[4] The epithet triloba in the species' scientific name refers to the flowers' three-lobed calices and doubly three-lobed corollas,[3] the shape not unlike a tricorne hat.
The common name of this species is variously spelled pawpaw, paw paw, paw-paw, and papaw. It probably derives from the Spanish papaya, an American tropical fruit (Carica papaya) sometimes also called "papaw",[5][6] perhaps because of the superficial similarity of their fruits.[citation needed] Asimina triloba has numerous other often very local common names, at least historically, including: wild banana, prairie banana, Indiana banana, Hoosier banana, West Virginia banana, Kansas banana, Kentucky banana, Michigan banana, Missouri banana, the poor man’s banana, Ozark banana, and banango.
[edit]Description
Asimina triloba is a large shrub or small tree growing to a height of 35 feet (11 m) (rarely to 45 feet or 14 m) with a trunks 8-12 inches (20–30 cm) or more in diameter. The large leaves of pawpaw trees are clustered symmetrically at the ends of the branches, giving a distinctive imbricated appearance to the tree's foliage.[3][7]
The leaves of the species are simple, alternate and spirally arranged, entire, deciduous, obovate-lanceolate, 10-12 inches (25–30 cm) long, 4-5 inches (10–13 cm) broad, and wedge-shaped at the base, with an acute apex and an entire margin, with the midrib and primary veins prominent. The petiolesare short and stout, with a prominent adaxial groove. Stipules are lacking. The expanding leaves are conduplicate, green, covered with rusty tomentum beneath, and hairy above; when fully grown they are smooth, dark green above, and paler beneath. When bruised, the leaves have a disagreeable odor similar to a green bell pepper. In autumn the leaves are a rusty yellow, which make spotting pawpaw groves possible from a long distance.[2][3][7]
Pawpaw flowers are perfect, about 1-2 inches (3–5 cm) across, rich red-purple or maroon when mature, with three sepals and six petals. They are borne singly on stout, hairy, axillary peduncles. The flowers are produced in early spring at the same time as or slightly before the new leaves appear, and have a faint fetid or yeasty smell.[2][3][7][8]
The fruit of the pawpaw is a large, yellowish-green to brown berry, 2–6 in (5–16 cm) long and 1–3 in (3–7 cm) broad, weighing from 0.7–18 oz (20–500 g), containing several brown seeds 1/2 to 1 in (15–25 mm) in diameter embedded in the soft, edible fruit pulp. The conspicuous fruits begin developing after the plants flower; they are initially green, maturing by September or October to yellow or brown. When mature, the heavy fruits bend the weak branches down.[2][3][7]
Other characteristics:
- Calyx: Sepals three, valvate in bud, ovate, acuminate, pale green, downy.[3][7]
- Corolla: Petals six, in two rows, imbricate in the bud. Inner row acute, erect, nectariferous. Outer row broadly ovate, reflexed at maturity. Petals at first are green, then brown, and finally become dull purple or maroon and conspicuously veiny.[3][7]
- Stamens: Indefinite, densely packed on the globular receptacle. Filaments short; anthers extrorse, two-celled, opening longitudinally.[7]
- Pistils: Several, on the summit of the receptacle, projecting from the mass of stamens. Ovary one-celled; stigma sessile; ovules many.[7]
- Branchlets: light brown, tinged with red, marked by shallow grooves.[7]
- Winter buds: Small, of two kinds, the leaf buds pointed and closely appressed to the twigs, and the flower buds round, brown, and fuzzy.[3]
- Bark: Light gray, sometimes blotched with lighter gray spots, sometimes covered with small excrescences, divided by shallow fissures. Inner bark tough, fibrous. The bark with a very disagreeable odor when bruised.[3][7]
- Wood: Pale, greenish yellow, sapwood lighter; light, soft, coarse-grained and spongy. Sp. gr., 0.3969; weight of cu ft 24.74 lb.[3][7]
[edit]Ecology
Asimina triloba, the pawpaw, commonly grows in floodplains and shady, rich bottomlands, where it often forms a dense, clonally spreading undergrowth in the forest, often appearing as a patch or thicket of individual small slender trees. Pawpaws are not the first to colonize a disturbed site (arriving roughly four years after a clearcut), but may become dominant and slow the establishment of oaks and hickories. Although shade-tolerant, pawpaws do not persist in undisturbedold growth forest. Pawpaws spread locally primarily by root suckers; sexual reproduction by seed does also occur, but at a fairly low rate.[9]
Pawpaw flowers are insect-pollinated, but fruit production is sometimes limited if few if any pollinators are attracted to the flower's faint, or sometimes non-existent scent.[citation needed] The flowers produce an odor similar to that of rotting meat to attract blowflies or carrion beetles for cross pollination.[citation needed]Other insects that are attracted to pawpaw flowers include scavenging fruit flies, carrion flies and beetles. Because of irregular fruit production, some[who?] believe pawpaw plants are self-incompatible, requiring cross-pollination between trees of different clones (patches).
The fruits of the pawpaw are eaten by a variety of mammals, including raccoons, gray foxes, opossums, squirrels, and black bears.[9]
The disagreeable-smelling leaves, twigs, and bark of pawpaws contain natural insecticides known as acetogenins.[10] Pawpaw leaves and twigs are seldom consumed by rabbits, deer, or goats,[11] or by many insects.[2] However, mules have been seen eating pawpaw leaves in Maryland.[12]
Larvae of the zebra swallowtail (Eurytides marcellus), a butterfly, feed exclusively on young leaves of Asimina triloba and various other pawpaw (Asimina)species, but never occur in great numbers on the plants.[11] Chemicals in the pawpaw leaves confer protection from predation throughout the butterfly's life, as trace amounts of acetogenins remain present, making them unpalatable to birds and other predators.[13]
[edit]Biochemistry
Pawpaw fruits are rich in fatty acids, the major one being octanoate. They also contain cis-δ9- and cis-δ11-hexadecenoate, cis-δ9-, cis-δ11- and cis-δ13-octadecenoate.
The seeds have been shown to contain the chemicals asimitrin (an adjacent ring-hydroxylated bis-tetrahydrofuran acetogenin) and 4-hydroxytrilobin (an adjacentbis-THF ring with two flanking hydroxyl groups and an α,β-unsaturated γ-lactone with a 4-hydroxyl group).[14] These chemicals seem to have selectivecytotoxicity against prostate adenocarcinoma (PC-3) and colon adenocarcinoma (HT-29) cell lines, thus may become a useful chemotherapeutic chemical for these types of cancer.
The leaves also contain toxic annonaceous acetogenins, making them impalatable to most insects. The one notable exception is the zebra swallowtail butterfly (Eurytides marcellus), whose larvae feed on the leaves of various species of Asimina, conferring protection from predation throughout the butterfly's life, as trace amounts of acetogenins remain present, making them unpalatable to birds and other predators.[13]
The bark of pawpaw trees contains other acetogenins, including asimin, asiminacin and asiminecin, which have been shown to be potent inhibitors ofmitochondrial NADH:ubiquinone oxidoreductase,[15] making A. triloba a promising source of pesticide and anti-tumour compounds.
[edit]Conservation status
On a global (range-wide) scale, the common pawpaw (Asimina triloba) has a NatureServe global conservation rank of G5 (Very Common).
In the United States, the species has a NatureServe national conservation rank of N5 (Very Common), but is considered a threatened species in New York, and an endangered species in New Jersey.
In Canada, where the species is found only in portions of southern Ontario, it has a NatureServe national conservation rank of N3 (Vulnerable), and a NatureServe subnational conservation rank of S3 (Vulnerable) in Ontario. The Ontario Ministry of Natural Resources has given the species a general status of "Sensitive", and its populations there are monitored.
In areas in which deer populations are dense, pawpaws appear to be becoming more abundant locally, since the deer avoid them but consume seedlings of most other woody plants.[12]
[edit]History
A strong candidate for the natural distribution of the common pawpaw (Asimina triloba) in North America, prior to the Ice Ages and lasting until roughly 10,000 years ago, was likely the then extant but now extinct megafauna of North America. (Such animals went extinct during the Quaternary extinction event.) With the arrival of humans, and the extinction of such megafauna for distributing Asimina triloba, the likely candidate for distributing these large fruit bearing plants likely became the newly-arrived humans.[16] The earliest documented mention of pawpaws is in the 1541 report of the Spanish de Soto expedition, who found Native Americans cultivating it east of the Mississippi River.[17]
Chilled pawpaw fruit was a favorite dessert of George Washington,[8][17] and Thomas Jefferson planted it at Monticello, his home in Virginia.[17]
The Lewis and Clark Expedition sometimes subsisted on pawpaws during their travels.[17]
[edit]Uses
[edit]Fruits
As described by horticulturist Barbara Damrosch, the fruit of the pawpaw "looks a bit like mango, but with pale yellow, custardly, spoonable flesh and black, easy-to-remove seeds."[18] Wild-collected pawpaw fruits, ripe in late August to mid September, have long been a favorite treat throughout the tree's extensive native range in eastern North America, and on occasion are sold locally at farmers' markets.[2][18] Pawpaw fruits have a sweet, custardish flavor somewhat similar to banana, mango, and cantaloupe,[2][3][19] varying significantly by source or cultivar,[2] with more protein than most fruits.[2] Nineteenth-century American agronomist E. Lewis Sturtevant described pawpaws as
... a natural custard, too luscious for the relish of most people"[12]
Ohio botanist William B. Werthner noted that
The fruit ... has a tangy wild-wood flavor peculiarly its own. It is sweet, yet rather cloying to the taste and a wee bit puckery – only a boy can eat more than one at a time.[3]
Fresh fruits of the pawpaw are commonly eaten raw, either chilled or at room temperature. However, they can be kept only 2–3 days at room temperature, or about a week if refrigerated.[8] The easily bruised pawpaw fruits do not ship well unless frozen.[2][18] Where pawpaws grow, the fruit pulp is also often used locally in baked dessert recipes, with pawpaw often substituted with volumetric equivalency in many banana-based recipes. Pawpaws may also be blended into ice cream[8] or included in pancakes.[8] Pawpaws are also used for juice-making,[citation needed] as either a fresh pawpaw drink[citation needed] or in drink mixtures (for example, a pawpaw, pineapple, banana, lime, lemon, and orange tea mix[citation needed]). The fruit pulp can also be made into a country wine.[citation needed]
In southern West Virginia, pawpaws are made into a native version of banana nut cake or fruit cake baked inside canning jars, then heat-sealed, reputedly keeping the food for at least a year;[citation needed] however, due to the risk of botulism, preserving cake in a canning jar is not recommended.[20]
[edit]Cultivation
Pawpaws have never been cultivated for their fruits on the scale of apples (Malus domestica) or peaches (Prunus persica), primarily because pawpaw fruits ripen to the point of fermentation soon after they are picked, and only frozen fruit will store or ship well. Other methods of preservation include dehydration, production of jams or jellies, and pressure canning (using the numerical values for bananas).
In recent years, cultivation of pawpaws for fruit production has attracted renewed interest, particularly among organic growers, as a native fruit with few to no pests, successfully grown withoutpesticides. The commercial cultivation and harvesting of pawpaws is strong in southeastern Ohio,[citation needed] and also being explored in Kentucky[2] and Maryland,[12] as well as various areas outside the species' native range, including California,[11] the Pacific Northwest.,[11] and Massachusetts[18]
Desirable kinds (cultivars) of pawpaw are propagated by chip budding or whip grafting. In cultivation, lack of successful pollination is the most common cause of poor fruiting. Cross-pollination of at least two different genetic varieties of the plant is recommended,[2] and growers often resort to hand pollination or to use of pollinator attractants such as spraying fish emulsion or hanging chicken necks or other meat near the open flowers to attract pollinators. While pawpaws are larval hosts for the zebra swallowtail butterfly, these caterpillars are usually present only at low density, and not detrimental to the foliage of the trees.[11]
The pawpaw is also gaining in popularity among landscapers and backyard gardeners because of the tree's distinctive growth habit, the appeal of its fresh fruit, and its relatively low maintenance needs once established. However, only container-grown pawpaws should be transplanted; use of bare-rooted pawpaws is not recommended, since their fragile root hairs tend to break off unless a cluster of moist soil is retained on the root mass.[8]
[edit]Insecticide source
The natural insecticides in the leaves, twigs, and bark of pawpaw trees can be used to make an organic pesticide.[10]
[edit]Wood
The wood of tree-sized pawpaws is not commercially valuable.
[edit]Habitat restoration
Pawpaws are sometimes included in ecological restoration plantings since this tree grows well in wet soil and has a strong tendency to form well-rooted colonial thickets. The pawpaw is particularly valued for establishing fast-growing vegetation in areas where frequent flooding might produce erosion, since their root systems help hold streambanks steady.[citation needed] Pawpaws grow well even in cold hollows with little exposure to winter sunlight.[citation needed]
[edit]Historical uses
The tough, fibrous inner bark of the pawpaw was used by Native Americans and settlers in the Midwest for making ropes, fishing nets, and mats,[3][12] and for stringing fish.[4]
No comments:
Post a Comment