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Overview

Brief Summary

Biology

It takes between 20 - 35 years for maidenhair trees to reach maturity and start bearing seeds. Pollen and ovules are produced in the spring on separate trees and, following fertilization, rounded seeds develop with a fleshy outer coat. These fall to the ground in the autumn and as the seed coat decays it exudes a rancid butter-like smell (3). Maidenhair trees can be extremely long-lived; the oldest recorded individual being 3,500 years old (3). Ginkgo trees have been utilised for traditional medicine in Japan and China for hundreds of years. The nuts are edible if cooked and are available for sale in markets throughout the Orient; the seeds are used to treat a variety of ailments from asthma to fever (3). The extract of the Ginkgo leaves is also believed to have medicinal properties and is one of the most popular herbal remedies in the West today (4). The leaf extract has been shown to increase circulation and is used to treat a range of ailments, including Alzheimer's disease (4).
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Description

Ginkgo biloba, or maidenhair tree, is renowned worldwide for its medicinal properties. This remarkable tree is known as a 'living fossil', as it is the sole survivor of an ancient group of trees that date back to beyond the time of the dinosaurs (3). The maidenhair tree remains virtually unchanged today and represents the only living bridge between 'higher' and 'lower' plants (between ferns and conifers) (3). Trees reach up to 40 metres in height and older individuals tend to have a more spreading appearance with irregular branches (3). The deeply fissured, brown bark may appear cork-like in older individuals (3). Male and female trees are separate; male pollen is borne on catkin-like cones amongst the leaves whilst female ovules are more rounded (3). After fertilisation, yellowish seeds develop with a fleshy outer seed coat that resembles a plum in appearance (3). The characteristic greenish-yellow leaves are fan-shaped and composed of two or more distinct lobes; the Latin species name biloba refers to this fact (3). The common name of maidenhair tree pertains to the similarity of the leaves to those of maidenhair ferns (Adiantum spp.) (3). In autumn, the leaves of the Ginkgo tree turn a beautiful golden hue before falling to the ground (3).
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Comprehensive Description

Ginkgo biloba



All of us may be unique but Raimundo Avelino is unique in a way few others in the world are – if the concept of being uniquely unique is not too much of a pleonasm. He is an elderly man who lives in the northwest of Brazil. He is also the last known native, fluent speaker of the Kiaxana language (Mosley, 2010). His death means the death of this language in human history and culture. We often have a fascination with the last of something: Hotel Terminus, The Last of the Mohicans, the last man standing, the last star fighter, Star Trek the Last Generation. The pianist Horowitz advertised himself as ‘the last romantic.’ Orwell’s 1984 was originally called The Last Man in Europe, and Mary Shelley wrote a novel actually called The Last Man.

The Ginkgo biloba is unique in that it is the last known surviving species of a once more abundant phylum called Ginkgophyta. Darwin himself coined the term ‘living fossil’ to describe such species. Some scientists now think the term should be abandoned as it has the wrong connotations. It implies that such species have stopped evolving, when in fact their evolutionary history may be quite dynamic (Gomez, 2013; and Mao, 2012).

The fossil record of ginkgos dates back to the early Permian (Koch, 2008). There are Jurassic fossils from the Asiatic part of Russia – though way back then this would have been part of the Laurasian supercontinent. They may have been very diverse and widespread during the Cretaceous with at least 16 genera; though fossils have limited geographic coverage, and it is difficult for taxonomists to distinguish species from just fossil leaves. During the Paleocene this diversity seems reduced. Gingkoes disappear from the fossil record in North America about 7 million years ago and from Europe 2.5 million years ago. No fossils are known from the Pleistocene. The last surviving population of Ginkgos was in the Dalou Mountains of China (Tang, 2012).

This plant is now more widespread thanks to human cultivation over the last 300 years. According to recent evidence they are most closely related to the cycads in the plant kingdom (Wu, 2013). Gingkoes are vascular plants (they have leaves that function as a plumbing system). The leaf veins look unique as they branch into 2 smaller veins; hence the name ‘biloba.’ Like other trees they produce wood by division of cambian cells – they have the same familiar division of sapwood (living tissue) which dies and becomes heartwood. A ginkgo tree is either male or female. The males produce pollen cones. The females produce stalks with ovules on the end that develop into seeds after pollination. Unlike flowering plants these ovules are exposed rather than being protected by the tissue we commonly call fruit. And unlike flowering plants the sperm are motile.

Now wind pollinated, there is evidence of insect pollination from the past (Penalvar, 2012). Cretaceous amber deposits in Spain (about 110 million years old) have yielded preserved thrips. These have pollen grains still attached. The theory is that these insects fed their larvae with pollen. The larvae would have lived in female ginkgos. The thrips would have transported pollen from male trees to the larvae, thus pollinating the trees as well. Another rare fossil find has yielded very old evidence of insect mimicry of gingko leafs (Ren, 2012). Both leaves and insects from Jurassic deposits of similar age show that the wings and abdomen of Juracimbrorophlebia ginkgfolia mimicked the ginkgo leaf.

The largest and oldest Ginkgo in the world may be the so-called ‘Grand Ginkgo King.’ (Xiang, 2009) This stands about 30 meters tall with a ground level diameter of 460 cm. The internal tissues with their growth rings of the oldest part of the multi-generational trunk are gone; but the age has been estimated as 4,000-4,500 years at a maximum. You can find it in the hamlet of Li Jiawan in China. Ginkgoes are now used as ornamental plants; in China and Japan the seed kernels are a foodstuff; and it has been claimed that the leaves have medicinal properties. It has been tested as a cure for diseases ranging from Alzheimer’s to MS but with inconclusive or controversial results. (There is a large literature of medical research. See for instance Posadzki, 2013.)

Like the ginkgo we are the last of a wider family. Neandertals and Homo erectus and ‘Denisovans’ and the hobbit-like fossil found in Java a few years ago are all extinct. We see the future only through a fog. We have no way of knowing, but it is at least conceivable that we will someday be extinct and the ginkgoes will survive us. This ‘living fossil’ may then give rise to other dynamic, evolving species. But then we would not be around to name them, in Kiaxana or any other language.







  • Gomez, Africa Et al. (2013) “Multiple global radiations in tadpole shrimp challenge the concept of ‘living fossils’” PeerJ, 2013; 1. http://peerj.com/articles/62
  • Koch, Marcus Et al. (2008) “Phylogeography of a living fossil” Molecular Phylogenetics and Evolution Vol.48, Issue 3, Sep. 2008, Pp.1094-1105.
  • Mao, Kangshan and Jianquan Liu. (2012) “Current relicts may be more dynamic in history than previously thought” New Phytologist Vol.196, Issue 3, Pp.329-331. Oct., 2012.
  • Mosely, Christopher (ed.) (2010) Atlas of the World’s Languages in Danger. 3rd ed., Paris, UNESCO Publishing. http://www.unesco.org/culture/en/endangeredlanguages/atlas
  • Penalvar, E. Et al. (2012) “Thrips pollination of Mesozoic gymnosperms” PNAS. Early edition 14 May 2012
  • Posadzki, Paul Et al. (2013) “Adverse effects of herbal medicines: an overview of systematic reviews” Clinical Medicine Feb.1, 2013, Vol.13, No.1, Pp.7-12
  • Ren, Dong Et al. “Jurassic mimicry between a hangingfly and a ginkgo from China” PNAS Dec.11, 2012.Vol.109.No.50, Pp.20514-20519. http://www.pnas.org/content/109/50/20514.short
  • Tang, Cindy Q. Et al. (2012) “Evidence for the persistence of wild Ginkgo biloba (Ginkgoaceae) populations in the Dalou Mountains southwest China” American Journal of Botany, Vol.99 No.8, Pp.1408-1414, Aug.2012. http://www.amjbot.org/content/99/8/1408.short
  • Wu, Chang-Shien Et al. (2013) “Chloroplast phylogenomics indicates that Ginkgo biloba is sister to Cycads” Genome Biology and Evolution. 5 (1): 243-254. http://gbe.oxfordjournals.org/content/5/1/243.full
  • Xiang, Zhu Et al. “The Li Jiawan Grand Ginkgo King” http://arnoldia.arboretum.harvard.edu/pdf/articles/2009-66-3-the-li-jiawan-grand-ginkgo-king.pdf
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Derivation of specific name

biloba: 2-loved, referring to the leaves
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Distribution

National Distribution

China

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

United States

Origin: Exotic

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

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Global Range: Known naturally "only in Chekiang Province, China" (Krussmann, 1985), but widely cultivated in Asia, Europe, and North America. The genus, if not this species itself, was formerly much more widespread, as shown by fossil records, but is now a narrow endemic as a naturally occurring plant,if not extirpated from the wild altogether.

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Range Description

The wild populations of this widely planted ornamental are apparently confined to Xitianmu Mt., Zhejiang. This is the only species in the genus. It is long-living and has an ancient geological record, appearing in the Jurassic.
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Perhaps native in NW Zhejiang (Tianmu Shan); widely and long cultivated below 2000 m in Anhui, Fujian, Gansu, Guizhou, Henan, Hebei, Hubei, Jiangsu, Jiangxi, Shaanxi, Shandong, Shanxi, Sichuan, Yunnan.
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Range

The attractive maidenhair tree has been widely planted as an ornamental, and cultivated individuals exist across the world (3). Trees were traditionally planted in temple gardens in Japan and China, but today are popular in towns worldwide and are even farmed in plantations for their medicinal properties (3). The survival of wild trees however is less secure; examples can be found in China on Mount Xitianmu in the Zhejiang Province, but it is unclear whether these are the last truly wild trees or descendents from temple gardens (3).
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Distribution: E. Asia. Cultivated elsewhere.
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C. China.
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Physical Description

Morphology

Description

Trees to 40 m tall; trunk to 4 m d.b.h.; bark light gray or grayish brown, longitudinally fissured especially on old trees; crown conical initially, finally broadly ovoid; long branchlets pale brownish yellow initially, finally gray, internodes (1-) 1.5-4 cm; short branchlets blackish gray, with dense, irregularly elliptic leaf scars; winter buds yellowish brown, ovate. Leaves with petiole (3-)5-8(-10) cm; blade pale green, turning bright yellow in autumn, to 13 × 8(-15) cm on young trees but usually 5-8 cm wide, those on long branchlets divided by a deep, apical sinus into 2 lobes each further dissected, those on short branchlets with undulate distal and margin notched apex. Pollen cones ivory colored, 1.2-2.2 cm; pollen sacs boat-shaped, with widely gaping slit. Seeds elliptic, narrowly obovoid, ovoid, or subglobose, 2.5-3.5 × 1.6-2.2 cm; sarcotesta yellow, or orange-yellow glaucous, with rancid odor when ripe; sclerotesta white, with 2 or 3 longitudinal ridges; endotesta pale reddish brown. Pollination Mar-Apr, seed maturity Sep-Oct.
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Physical Description

Tree, Deciduous, Dioecious, Habit erect, Trees without or rarely having knees, Primary plant stem smooth, Tree with bark rough or scaly, Young shoots 3-dimensional, Buds not resinous, Leaves fan-shaped, Leaves broad, Leaves alternate, Non-needle-like leaf margins entire, Non-needle-like leaf margins dentate or serrate, Leaf apex obtuse, Leaf apex mucronulate, Leaves < 5 cm long, Leaves > 5 cm long, Leaves < 10 cm long, Leaves yellow-green above, Leaves yellow-green below, Leaves not blue-green, Scale leaves without raised glands, Twigs glabrous, Twigs not viscid, Twigs without peg-like projections or large fascicles after needles fall, Seeds within cone, Aril light green, Aril dark green, Berry-like cones reddish, Bracts of seed cone included, Seeds tan, Seeds brown, Seeds wingless.
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Description

Dioecious. Tree up to 30 m tall. Leaves foliaceous with flabellate venation. Male cones on dwarf shoots in catkin‑like clusters; microsophylls stalked. Sporangia usually 2, pendant. Female cone on dwarf shoots. Ovules 2. terminal, usually only I developing into a seed.
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Elevation Range

1300 m
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Description

Trees to 30 m. Crown somewhat ovoid to obovoid, tending to be asymmetric, primary branches ascending at ca. 45° from trunk. Long shoots faintly striate; spurs thick, knoblike or to 3 cm, gray, covered with bud-scale scars. Buds brown, globose, scales imbricate, margins scarious. Leaves fan-shaped, glabrous except for tuft of hairs in axils, blades 2--9.5 × 2--12 cm, mostly 1.5 times wider than long, apices cleft to truncate; venation dichotomous, appearing parallel; leaf scars semicircular; petioles channeled on adaxial surface, 2.5--8.5 cm. Seeds obovoid to ellipsoid, yellow to orange, 2.3--2.7 × 1.9--2.3 cm, mostly 1.1--1.2 times longer than broad, glaucous, rugose, with apical scar, maturing in single season, usually 1 per peduncle, occasionally polyembryonic, outer coat foul-smelling; peduncles orange, glaucous, ridged, 3--9.5 cm, collar broadly elliptic, 7.2--8.6 mm broad. 2 n = 24.
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Diagnostic Description

Synonym

Salisburia adiantifolia Smith; S. biloba (Linnaeus) Hoffmansegg.
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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
Scattered in broadleaved forests up to 1,100 m. This is the only species in the genus. It is long-living and has an ancient geological record, appearing in the Jurassic.

Systems
  • Terrestrial
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* Scattered in broad-leaved forests and valleys on acidic, well-drained, yellow loess (pH = 5-5.5); 300-1100 m.
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The maidenhair tree is most suited to moist, deep, sandy soils in full sunlight but is extremely adaptable to a range of stressful conditions. Indeed, it was the first tree in the vicinity of Hiroshima to bud after the atomic bomb of 1945 (3).
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A sparingly cultivated ornamental tree native to eastern China. Common name: `Maiden hair tree'.
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Associations

In Great Britain and/or Ireland:
Foodplant / saprobe
mainly hypophyllous, erumpent, becoming superficial, often circinate telium of Bartheletia paradoxa is saprobic on dead, recently fallen leaf of Ginkgo biloba
Remarks: season: autumn

Foodplant / saprobe
fruitbody of Ganoderma australe is saprobic on dead trunk of Ginkgo biloba

Foodplant / feeds on
pycnidium of Conothyrium coelomycetous anamorph of Microsphaeropsis olivacea feeds on Ginkgo biloba

Foodplant / saprobe
pycnidium of Phomopsis coelomycetous anamorph of Phomopsis occulta var. ginkgoina is saprobic on dead twig of Ginkgo biloba

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Population Biology

Number of Occurrences

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 1 - 5

Comments: Reportedly extant in a few natural stands in China (Ms. Wang Si Yu, Acad. Sinica, Peking, discussion w/ LEM 10Jun 86).

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Conservation

Conservation Status

National NatureServe Conservation Status

China

Rounded National Status Rank: N1 - Critically Imperiled

United States

Rounded National Status Rank: NNA - Not Applicable

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NatureServe Conservation Status

Rounded Global Status Rank: G1 - Critically Imperiled

Reasons: Very rare, but still reportedly extant, as natural stands in China. Cultivated, rarely escaped in N. America.

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IUCN Red List Assessment


Red List Category
EN
Endangered

Red List Criteria
B1+2c

Version
2.3

Year Assessed
1998
  • Needs updating

Assessor/s
Sun, W.

Reviewer/s

Contributor/s

History
  • 1997
    Rare
    (Walter and Gillett 1998)
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Status

Classified as Endangered (EN - B1+2c) on the IUCN Red List 2002 (1).
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Threats

Comments: The trees themselves are unusually resistant to air pollution, diseases, and insect damage; information on threats to the species in its natural habitat not available.

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The maidenhair tree was thought to have become extinct, similarly to the other members of its ancient linage, until it was discovered in Japan in 1691 (3). This fascinating species had persisted in the gardens of temples in the East and the first seeds were brought to Europe in the 1700s (3). The loss of the Ginkgo from the wild is likely to have been a result of deforestation, which has swept through the region (1).
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Management

Biological Research Needs: Not known whether any US stands are self-perpetuating outside cultivation.

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Conservation Actions

Conservation Actions
The species has been widespread in cultivation for several centuries.
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Conservation

It is uncertain whether the maidenhair tree still persists in the wild and at present there are no conservation projects in place. Cultivated trees are found throughout the world however, and a multi-million dollar industry has cashed in on the leave's medicinal properties (3). As a result, it is likely that this ancient tree will stand the test of time.
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Wikipedia

Ginkgo biloba

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Ginkgo (Ginkgo biloba; in Chinese and Japanese 銀杏, pinyin romanization: yín xìng, Hepburn romanization: ichō or ginnan), also spelled gingko and known as the Maidenhair Tree, is a unique species of tree with no close living relatives. The tree is widely cultivated and introduced, since an early period in human history, and has various uses as a food and traditional medicine.

Contents

Description

Ginkgoes are very large trees, normally reaching a height of 20–35 m (66–115 feet), with some specimens in China being over 50 m (164 feet). The tree has an angular crown and long, somewhat erratic branches, and is usually deep rooted and resistant to wind and snow damage. Young trees are often tall and slender, and sparsely branched; the crown becomes broader as the tree ages. During autumn, the leaves turn a bright yellow, then fall, sometimes within a short space of time (1–15 days). A combination of resistance to disease, insect-resistant wood and the ability to form aerial roots and sprouts makes ginkgos long-lived, with some specimens claimed to be more than 2,500 years old.

Ginkgo is a relatively shade-intolerant species that (at least in cultivation) grows best in environments that are well-watered and well-drained. The species shows a preference for disturbed sites; in the "semi-wild" stands at Tian Mu Shan, many specimens are found along stream banks, rocky slopes, and cliff edges. Accordingly, Ginkgo retains a prodigious capacity for vegetative growth. It is capable of sprouting from embedded buds near the base of the trunk (lignotubers, or basal chi chi) in response to disturbances, such as soil erosion. Old individuals are also capable of producing aerial roots (chi chi) on the undersides of large branches in response to disturbances such as crown damage; these roots can lead to successful clonal reproduction upon contacting the soil. These strategies are evidently important in the persistence of Ginkgo; in a survey of the "semi-wild" stands remaining in Tian Mu Shan, 40% of the Ginkgo specimens surveyed were multi-stemmed, and few saplings were present.[3]

Trunk bark

Stem

Ginkgo branches grow in length by growth of shoots with regularly spaced leaves, as seen on most trees. From the axils of these leaves, "spur shoots" (also known as short shoots) develop on second-year growth. Short shoots have very short internodes (so they may grow only one or two centimeters in several years) and their leaves are usually unlobed. They are short and knobby, and are arranged regularly on the branches except on first-year growth. Because of the short internodes, leaves appear to be clustered at the tips of short shoots, and reproductive structures are formed only on them (see pictures below - seeds and leaves are visible on short shoots). In Ginkgos, as in other plants that possess them, short shoots allow the formation of new leaves in the older parts of the crown. After a number of years, a short shoot may change into a long (ordinary) shoot, or vice versa.

Leaves

Ginkgo leaves in autumn

The leaves are unique among seed plants, being fan-shaped with veins radiating out into the leaf blade, sometimes bifurcating (splitting) but never anastomosing to form a network.[4] Two veins enter the leaf blade at the base and fork repeatedly in two; this is known as dichotomous venation. The leaves are usually 5–10 cm (2-4 inches), but sometimes up to 15 cm (6 inches) long. The old popular name "Maidenhair tree" is because the leaves resemble some of the pinnae of the Maidenhair fern Adiantum capillus-veneris.

Leaves of long shoots are usually notched or lobed, but only from the outer surface, between the veins. They are borne both on the more rapidly-growing branch tips, where they are alternate and spaced out, and also on the short, stubby spur shoots, where they are clustered at the tips.

Reproduction

Ginkgos are dioecious, with separate sexes, some trees being female and others being male. Male plants produce small pollen cones with sporophylls each bearing two microsporangia spirally arranged around a central axis.

Female plants do not produce cones. Two ovules are formed at the end of a stalk, and after pollination, one or both develop into seeds. The seed is 1.5–2 cm long. Its fleshy outer layer (the sarcotesta) is light yellow-brown, soft, and fruit-like. It is attractive in appearance, but contains butanoic acid[5] (also known as butyric acid) and smells like rancid butter (which contains the same chemical) or feces[6] when fallen. Beneath the sarcotesta is the hard sclerotesta (what is normally known as the "shell" of the seed) and a papery endotesta, with the nucellus surrounding the female gametophyte at the center.[7]

The fertilization of ginkgo seeds occurs via motile sperm, as in cycads, ferns, mosses and algae. The sperm are large (about 250-300 micrometres) and are similar to the sperm of cycads, which are slightly larger. Ginkgo sperm were first discovered by the Japanese botanist Sakugoro Hirase in 1896.[8] The sperm have a complex multi-layered structure, which is a continuous belt of basal bodies that form the base of several thousand flagella which actually have a cilia-like motion. The flagella/cilia apparatus pulls the body of the sperm forwards. The sperm have only a tiny distance to travel to the archegonia, of which there are usually two or three. Two sperm are produced, one of which successfully fertilizes the ovule. Although it is widely held that fertilization of ginkgo seeds occurs just before or after they fall in early autumn,[4][7] embryos ordinarily occur in seeds just before and after they drop from the tree.[9]

Distribution and habitat

Although Ginkgo biloba and other species of the genus were once widespread throughout the world, their range shrank until by two million years ago it was restricted to a small area of China. For centuries it was thought to be extinct in the wild, but is now known to grow in at least two small areas in Zhejiang province in Eastern China, in the Tian Mu Shan Reserve. However, recent studies indicate high genetic uniformity among ginkgo trees from these areas, arguing against a natural origin of these populations and suggesting that the ginkgo trees in these areas may have been planted and preserved by Chinese monks over a period of about 1,000 years.[10] Whether native ginkgo populations still exist has not been demonstrated unequivocally.

Where it occurs in the wild it is found infrequently in deciduous forests and valleys on acidic loess (i.e. fine, silty soil) with good drainage. The soil it inhabits is typically in the pH range of 5 to 5.5.[11]

In many areas of China it has been long cultivated and it is common in the southern third of the country.[11] It has also been commonly cultivated in North America for over 200 years, but during that time it has never become significantly naturalised.[12]

Taxonomy and naming

Ginkgo tree in autumn
Ginkgo tree in late autumn

The species was initially described by Linnaeus in 1771, the specific epithet biloba derived from the Latin bis 'two' and loba 'lobed', referring to the shape of the leaves.[13] Two names for the species recognise the botanist Richard Salisbury, a placement by Nelson as Pterophyllus salisburiensis and the earlier Salisburia adiantifolia proposed by James Edward Smith. The epithet of the latter may have been intended to denote a characteristic resembling Adiantum, the genus of maidenhair ferns.[14]

The relationship of Ginkgo to other plant groups remains uncertain. It has been placed loosely in the divisions Spermatophyta and Pinophyta, but no consensus has been reached. Since Ginkgo seeds are not protected by an ovary wall, it can morphologically be considered a gymnosperm. The apricot-like structures produced by female ginkgo trees are technically not fruits, but are seeds that have a shell that consists of a soft and fleshy section (the sarcotesta), and a hard section (the sclerotesta).

The ginkgo is classified in its own division, the Ginkgophyta, comprising the single class Ginkgoopsida, order Ginkgoales, family Ginkgoaceae, genus Ginkgo and is the only extant species within this group. It is one of the best-known examples of a living fossil, because Ginkgoales other than G. biloba are not known from the fossil record after the Pliocene.[15][16]

Etymology

The older Chinese name for this plant is 銀果 yínguǒ ('silver fruit'). The most usual names today are 白果 bái guǒ ('white fruit') and 銀杏 yínxìng ('silver apricot'). The former name was borrowed directly in Vietnamese (as bạch quả). The latter name was borrowed in Japanese (as ぎんなん "ginnan") and Korean (as 은행 "eunhaeng"), when the tree itself was introduced from China.

The scientific name Ginkgo appears to be due to a process akin to folk etymology. Chinese characters typically have multiple pronunciations in Japanese, and the characters 銀杏 used for ginnan can also be pronounced ginkyō. Engelbert Kaempfer, the first Westerner to see the species in 1690, wrote down this pronunciation in his Amoenitates Exoticae (1712) with the "awkward" spelling "Ginkgo". This appears to be a simple error of Kaempfer, taking his spelling of other Japanese words into account, a more precise romanization would have been "Ginkio" or "Ginkjo".[17]

Palaeontology

Ginkgo biloba Eocene leaf from the MacAbee, B.C., Canada.

The Ginkgo is a living fossil, with fossils recognisably related to modern Ginkgo from the Permian, dating back 270 million years. The most plausible ancestral group for the order Ginkgoales is the Pteridospermatophyta, also known as the "seed ferns," specifically the order Peltaspermales. The closest living relatives of the clade are the cycads,[18] which share with the extant G. biloba the characteristic of motile sperm. Fossils attributable to the genus Ginkgo first appeared in the Early Jurassic, and the genus diversified and spread throughout Laurasia during the middle Jurassic and Early Cretaceous. It declined in diversity as the Cretaceous progressed, and by the Paleocene, Ginkgo adiantoides was the only Ginkgo species left in the Northern Hemisphere while a markedly different (and poorly documented) form persisted in the Southern Hemisphere. At the end of the Pliocene, Ginkgo fossils disappeared from the fossil record everywhere except in a small area of central China where the modern species survived. It is doubtful whether the Northern Hemisphere fossil species of Ginkgo can be reliably distinguished. Given the slow pace of evolution and morphological similarity between members of the genus, there may have been only one or two species existing in the Northern Hemisphere through the entirety of the Cenozoic: present-day G. biloba (including G. adiantoides) and G. gardneri from the Paleocene of Scotland.[19]

At least morphologically, G. gardneri and the Southern Hemisphere species are the only known post-Jurassic taxa that can be unequivocally recognised. The remainder may have been ecotypes or subspecies. The implications would be that G. biloba had occurred over an extremely wide range, had remarkable genetic flexibility and, though evolving genetically, never showed much speciation. While it may seem improbable that a species may exist as a contiguous entity for many millions of years, many of the Ginkgo's life-history parameters fit. These are: extreme longevity; slow reproduction rate; (in Cenozoic and later times) a wide, apparently contiguous, but steadily contracting distribution coupled with, as far as can be demonstrated from the fossil record, extreme ecological conservatism (restriction to disturbed streamside environments).[20]

Fossil Ginkgo leaves from the Jurassic of England

Modern-day G. biloba grows best in environments that are well-watered and drained,[21] and the extremely similar fossil Ginkgo favored similar environments: the sediment record at the majority of fossil Ginkgo localities indicates it grew primarily in disturbed environments along streams and levees.[20] Ginkgo therefore presents an "ecological paradox" because while it possesses some favorable traits for living in disturbed environments (clonal reproduction) many of its other life-history traits (slow growth, large seed size, late reproductive maturity) are the opposite of those exhibited by modern plants that thrive in disturbed settings.[22]

Given the slow rate of evolution of the genus, it is possible that Ginkgo represents a pre-angiosperm strategy for survival in disturbed streamside environments. Ginkgo evolved in an era before flowering plants, when ferns, cycads, and cycadeoids dominated disturbed streamside environments, forming a low, open, shrubby canopy. Ginkgo's large seeds and habit of "bolting" - growing to a height of 10 m before elongating its side branches - may be adaptions to such an environment. The fact that diversity in the genus Ginkgo drops through the Cretaceous (along with that of ferns, cycads, and cycadeoids) at the same time that flowering plants were on the rise, supports the notion that flowering plants with better adaptations to disturbance displaced Ginkgo and its associates over time.[23]

Ginkgo has been used for classifying plants with leaves that have more than four veins per segment, while Baiera for those with fewer than four veins per segment. Sphenobaiera has been used to classify plants with a broadly wedge-shaped leaf that lacks a distinct leaf stem. Trichopitys is distinguished by having multiple-forked leaves with cylindrical (not flattened) thread-like ultimate divisions; it is one of the earliest fossils ascribed to the Ginkgophyta.

Cultivation and uses

Ginkgo has long been cultivated in China; some planted trees at temples are believed to be over 1,500 years old. The first record of Europeans encountering it is in 1690 in Japanese temple gardens, where the tree was seen by the German botanist Engelbert Kaempfer. Because of its status in Buddhism and Confucianism, the Ginkgo is also widely planted in Korea and parts of Japan; in both areas, some naturalization has occurred, with Ginkgos seeding into natural forests.

In some areas, most intentionally planted Ginkgos are male cultivars grafted onto plants propagated from seed, because the male trees will not produce the malodorous seeds. The popular cultivar 'Autumn Gold' is a clone of a male plant.

Ginkgos adapt well to the urban environment, tolerating pollution and confined soil spaces.[24] They rarely suffer disease problems, even in urban conditions, and are attacked by few insects.[25][26] For this reason, and for their general beauty, ginkgos are excellent urban and shade trees, and are widely planted along many streets.

Ginkgos are also popular subjects for growing as penjing and bonsai; they can be kept artificially small and tended over centuries. Furthermore, the trees are easy to propagate from seed.

Extreme examples of the Ginkgo's tenacity may be seen in Hiroshima, Japan, where six trees growing between 1–2 km from the 1945 atom bomb explosion were among the few living things in the area to survive the blast (photos and details). While almost all other plants (and animals) in the area were destroyed, the ginkgos, though charred, survived and were soon healthy again. The trees are alive to this day.

The ginkgo leaf is the symbol of the Urasenke school of Japanese tea ceremony. The tree is the national tree of China.

Culinary use

Ginkgo seeds with sarcotesta removed

The nut-like gametophytes inside the seeds are particularly esteemed in Asia, and are a traditional Chinese food. Ginkgo nuts are used in congee, and are often served at special occasions such as weddings and the Chinese New Year (as part of the vegetarian dish called Buddha's delight). In Chinese culture, they are believed to have health benefits; some also consider them to have aphrodisiac qualities. Japanese cooks add Ginkgo seeds (called ginnan) to dishes such as chawanmushi, and cooked seeds are often eaten along with other dishes.

When eaten in large quantities (over 50 seeds) or over a long period, especially by children[27] the gametophyte (meat) of the seed can cause poisoning by MPN (4-methoxypyridoxine). MPN is heat stable and not destroyed by cooking.[27] Studies have demonstrated that convulsions caused by MPN can be prevented or terminated with pyridoxine.

Some people are sensitive to the chemicals in the sarcotesta, the outer fleshy coating. These people should handle the seeds with care when preparing the seeds for consumption, wearing disposable gloves. The symptoms are allergic contact dermatitis[28][29] or blisters similar to that caused by contact with poison ivy. However, seeds with the fleshy coating removed are mostly safe to handle.

Ginkgo biloba in Tournai, (Belgium).

Medicinal uses

Extracts of Ginkgo leaves contain flavonoid glycosides and terpenoids (ginkgolides, bilobalides) and have been used pharmaceutically. Ginkgo supplements are usually taken in the range of 40–200 mg per day. Recently, careful clinical trials have shown Ginkgo to be ineffective in treating dementia or preventing the onset of Alzheimer's Disease in normal people.[30][31]

In memory enhancement

Ginkgo is believed to have nootropic properties, and is mainly used as memory[32] and concentration enhancer, and anti-vertigo agent. However, studies differ about its efficacy. The largest and longest independent clinical trial to assess Ginkgo biloba’s ability to prevent memory loss has found that the supplement does not prevent or delay dementia or Alzheimer’s disease.[33] Some controversy has arisen over the conclusions drawn by some studies that were funded by a firm which marketed Ginkgo.[34]

In 2002 a long-anticipated paper appeared in JAMA titled "Ginkgo for memory enhancement: a randomized controlled trial." This Williams College study, sponsored by the National Institute on Aging rather than Schwabe, examined the effects of ginkgo consumption on healthy volunteers older than 60. The conclusion, now cited in the National Institutes of Health's ginkgo fact sheet, said: "When taken following the manufacturer's instructions, ginkgo provides no measurable benefit in memory or related cognitive function to adults with healthy cognitive function."[35] ... The impact of this seemingly damning assessment, however, was ameliorated by the almost simultaneous publication of a Schwabe-sponsored study in the less prestigious journal Human Psychopharmacology. This rival study, conducted at Jerry Falwell's Liberty University, was rejected by JAMA, and came to a very different—if not exactly sweeping—conclusion: There was ample evidence to support "the potential efficacy of Ginkgo biloba EGb 761 in enhancing certain neuropsychological/memory processes of cognitively intact older adults, 60 years of age and over."

According to some studies, Ginkgo can significantly improve attention in healthy individuals.[36][37] In one such study, the effect was almost immediate and reaches its peak in 2.5 hours after the intake.[38]

In dementia

Ginkgo has been proposed as a treatment for Alzheimer's disease on the basis of positive preclinical results in mice[39] and a 2006 study that found 160 mg of ginkgo extract as effective as a daily 5 mg dose of the cholinesterase inhibitor donepezil in human subjects.[40] However, a randomized controlled clinical trial published in JAMA in 2008 found it ineffective at treating dementia in humans.[30][41] A second randomized controlled trial, published in JAMA in 2009, similarly found no benefit from ginkgo in preventing cognitive decline or dementia.[31] A more recent meta-analysis of nine studies of ginkgo for use in dementia concluded that it was more effective than placebo although, like other dementia drugs, the clinical significance of these moderate effects was difficult to quantify.[42]

In other symptoms

Out of the many conflicting research results, Ginkgo extract may have three effects on the human body: improvement in blood flow (including microcirculation in small capillaries) to most tissues and organs; protection against oxidative cell damage from free radicals; and blockage of many of the effects of platelet-activating factor (platelet aggregation, blood clotting)[43] that have been related to the development of a number of cardiovascular, renal, respiratory and central nervous system disorders. Ginkgo can be used for intermittent claudication.

Some studies suggest a link between ginkgo and the easing of the symptoms of tinnitus.[44]

The World Health Organization[45] reports that the medicinal uses of ginkgo biloba that are supported by clinical data include treatment of the effects mild to moderate cerebrovascular insufficiency [46] as well as the effects of peripheral arterial occlusive diseases.[47] Cerebrovascular insufficiency, i.e., insufficient blood flow to the brain, may manifest itself as such memory deficit, disturbed concentration or headaches. Peripheral arterial occlusive diseases are those in which the blood flow to the smaller arteries are restricted and may include claudication, i.e., painful walking, and Raynaud's disease, a condtion in which the extremities such as fingers, toes, nose or ears, feel numb and cold.

Preliminary studies suggest that Ginkgo may be of benefit in multiple sclerosis, showing modest improvements in cognition[48] and fatigue[48] without increasing rates of serious adverse events in this population.

A study conducted in 2003 by the Department of Dermatology, Postgraduate Institute of Medical Education and Research in Chandigarh, India concluded that Ginkgo is an effective treatment for arresting the development of vitiligo.[49]

Side effects

Ginkgo may have undesirable effects, especially for individuals with blood circulation disorders and those taking anticoagulants such as ibuprofen, aspirin, or warfarin, although recent studies have found that ginkgo has little or no effect on the anticoagulant properties or pharmacodynamics of warfarin in healthy subjects.[50][51] Ginkgo should also not be used by people who are taking certain types of antidepressants (monoamine oxidase inhibitors and selective serotonin reuptake inhibitors[52][53]) or by pregnant women, without first consulting a doctor.

Ginkgo side effects and cautions include: possible increased risk of bleeding, gastrointestinal discomfort, nausea, vomiting, diarrhea, headaches, dizziness, heart palpitations, and restlessness.[53][54] If any side effects are experienced, consumption should be stopped immediately.

Allergic precautions and contraindications to use

People taking pharmaceutical blood thinners such as warfarin or coumadin should consult with their doctor before taking Gingko biloba extracts, as it acts as an anti-coagulant.

The presence of amentoflavone in Gingko biloba leaves would indicate a potential for interactions with many medications through the strong inhibition of CYP3A4 and CYP2C9; however, there is a lack of any empirical evidence supporting this. It is possible that the concentration of amentoflavone found even in commercial Gingko biloba extracts is too low to be pharmacologically active.

Ginkgo biloba in Morlanwelz-Mariemont Park, Belgium

Ginkgo biloba leaves also contain long-chain alkylphenols together with the extremely potent allergens, the urushiols (similar to poison ivy).[29] Individuals with a history of strong allergic reactions to poison ivy, mangoes, and other urushiol-producing plants are more likely to experience an adverse reaction when consuming Ginkgo-containing pills, combinations, or extracts.

See also

References

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  2. ^ Sun (1998). 'Ginkgo biloba'. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 11 May 2006. Listed as Endangered (EN B1+2c v2.3)
  3. ^ Royer et al., pp. 86-87
  4. ^ a b Ginkgoales: More on Morphology
  5. ^ Raven, Peter H.; Ray F. Evert; Susan E. Eichhorn (2005). Biology of Plants (7th ed.). New York: W. H. Freeman and Company. pp. 429–430. ISBN 0716710072. 
  6. ^ Solomon, et al. "Biology" p.523 ISBN 0534492762
  7. ^ a b Laboratory IX -- Ginkgo, Cordaites, and the Conifers
  8. ^ History of Discovery of Spermatozoids In Ginkgo biloba and Cycas revoluta
  9. ^ Holt, B. F.; Rothwell, G. W. (1997). "Is Ginkgo biloba (Ginkgoaceae) Really an Oviparous Plant?". American Journal of Botany 84 (6): 870–872. doi:10.2307/2445823. http://jstor.org/stable/2445823. 
  10. ^ Shen, L; Chen, X-Y; Zhang, X; Li, Y-Y; Fu, C-X; Qiu, Y-X (2004). "Genetic variation of Ginkgo biloba L. (Ginkgoaceae) based on cpDNA PCR-RFLPs: inference of glacial refugia". Heredity 94 (4): 396–401. doi:10.1038/sj.hdy.6800616. PMID 15536482. 
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  12. ^ Whetstone, R. David (2006). "Ginkgo biloba". In Flora of North America Editorial Committee, eds. 1993+. Flora of North America. 2. New York & Oxford: Oxford University Press. http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=200005235. 
  13. ^ Simpson DP (1979). Cassell's Latin Dictionary (5 ed.). London: Cassell Ltd.. pp. 883. ISBN 0-304-52257-0. 
  14. ^ Chandler, Brian (2000). "Ginkgo - origins". Ginkgo pages. http://imaginatorium.org/sano/ginkgo2.htm. Retrieved 22 November 2010. 
  15. ^ Zhou, Zhiyan; Zheng, Shaolin (2003). "Palaeobiology: The missing link in Ginkgo evolution". Nature 423 (6942): 821–2. doi:10.1038/423821a. PMID 12815417. 
  16. ^ Julie Jalalpour, Matt Malkin, Peter Poon, Liz Rehrmann, Jerry Yu (1997). "Ginkgoales: Fossil Record". University of California, Berkeley. http://www.ucmp.berkeley.edu/seedplants/ginkgoales/ginkgofr.html. Retrieved 3 June 2008. 
  17. ^ Faculty of languages and cultures, Kyushu University Japan
  18. ^ Royer et al., p.84
  19. ^ Royer et al., p.85
  20. ^ a b Royer et al., p.91
  21. ^ Royer et al., p.87
  22. ^ Royer et al., p.92
  23. ^ Royer et al., p.93
  24. ^ Gilman, Edward F. and Dennis G. Watson (1993). "Ginkgo biloba 'Autumn Gold'" (PDF). US Forest Service. http://hort.ufl.edu/trees/GINBILB.pdf. Retrieved 29 March 2008. 
  25. ^ Boland, Timothy, Laura E. Coit, Marty Hair (2002). Michigan Gardener's Guide. Cool Springs Press. ISBN 1930604203. http://books.google.com/?id=8Ymg47Ccz0kC&pg=PA199&vq=ginkgo&dq=ginkgo+tree+disease. 
  26. ^ "Examples of Plants with Insect and Disease Tolerance". SULIS - Sustainable Urban Landscape Information Series. University of Minnesota. http://www.sustland.umn.edu/design/insect.htm. Retrieved 29 March 2008. 
  27. ^ a b Ginkgo Seed Poisoning. PEDIATRICS Vol. 109 No. 2 February 2002, pp. 325-327 [1]
  28. ^ Lepoittevin, J. -P.; Benezra, C.; Asakawa, Y. (1989). "Allergic contact dermatitis to Ginkgo biloba L.: relationship with urushiol". Archives of Dermatological Research 281 (4): 227–30. doi:10.1007/BF00431055. PMID 2774654. 
  29. ^ a b Schötz, Karl (2004). "Quantification of allergenic urushiols in extracts ofGinkgo biloba leaves, in simple one-step extracts and refined manufactured material(EGb 761)". Phytochemical Analysis 15 (1): 1–8. doi:10.1002/pca.733. PMID 14979519. 
  30. ^ a b Dekosky, S. T.; Williamson, J. D.; Fitzpatrick, A. L.; Kronmal, R. A.; Ives, D. G.; Saxton, J. A.; Lopez, O. L.; Burke, G. et al. (2008). "Ginkgo biloba for Prevention of Dementia: A Randomized Controlled Trial". JAMA: the Journal of the American Medical Association 300: 2253–62. doi:10.1001/jama.2008.683. 
  31. ^ a b Snitz, B. E.; O'Meara, E. S.; Carlson, M. C.; Arnold, A. M.; Ives, D. G.; Rapp, S. R.; Saxton, J.; Lopez, O. L. et al. (2009). "Ginkgo biloba for Preventing Cognitive Decline in Older Adults: A Randomized Trial". JAMA: the Journal of the American Medical Association 302: 2663–70. doi:10.1001/jama.2009.1913. 
  32. ^ Mahadevan, S.; Park, Y. (2007). "Multifaceted Therapeutic Benefits of Ginkgo biloba L.: Chemistry, Efficacy, Safety, and Uses". Journal of Food Science 73 (1): R14–9. doi:10.1111/j.1750-3841.2007.00597.x. PMID 18211362. 
  33. ^ Rabin, Roni Caryn (November 18, 2008). "Ginkgo biloba Ineffective Against Dementia, Researchers Find". The New York Times. http://www.nytimes.com/2008/11/19/health/research/18gingko.html. Retrieved 12 October 2009. 
  34. ^ Koerner, Brendan I.. "Ginkgo Biloba? Forget About It.". Slate. http://www.slate.com/id/2165042/pagenum/all/. Retrieved 12 October 2009. 
  35. ^ http://nccam.nih.gov/health/ginkgo/D290_Herbs.pdf
  36. ^ Elsabagh, Sarah; Hartley, David E.; Ali, Osama; Williamson, Elizabeth M.; File, Sandra E. (2005). "Differential cognitive effects of Ginkgo biloba after acute and chronic treatment in healthy young volunteers". Psychopharmacology 179 (2): 437–46. doi:10.1007/s00213-005-2206-6. PMID 15739076. 
  37. ^ BBC News: Herbal remedies "boost brain power"
  38. ^ Kennedy, David O.; Scholey, Andrew B.; Wesnes, Keith A. (2000). "The dose-dependent cognitive effects of acute administration of Ginkgo biloba to healthy young volunteers". Psychopharmacology 151 (4): 416–23. doi:10.1007/s002130000501. PMID 11026748. 
  39. ^ Ginkgo Extract Has Multiple Actions on Alzheimer Symptoms Newswise, Retrieved on August 25, 2008.
  40. ^ Mazza, M.; Capuano, A.; Bria, P.; Mazza, S. (2006). "Ginkgo biloba and donepezil: a comparison in the treatment of Alzheimer's dementia in a randomized placebo-controlled double-blind study". European Journal of Neurology 13 (9): 981–5. doi:10.1111/j.1468-1331.2006.01409.x. PMID 16930364. 
  41. ^ "Ginkgo 'does not treat dementia'". BBC News. June 16, 2008. http://news.bbc.co.uk/2/hi/health/7453167.stm. 
  42. ^ Weinmann, S; Roll, S; Schwarzbach, C; Vauth, C; Willich, SN (2010). "Effects of Ginkgo biloba in dementia: systematic review and meta-analysis.". BMC geriatrics 10: 14. doi:10.1186/1471-2318-10-14. PMID 20236541. 
  43. ^ Smith, P; MacLennan, K; Darlington, CL (1996). "The neuroprotective properties of the Ginkgo biloba leaf: a review of the possible relationship to platelet-activating factor (PAF)". Journal of Ethnopharmacology 50 (3): 131–9. doi:10.1016/0378-8741(96)01379-7. PMID 8691847. 
  44. ^ http://www.bixby.org/faq/tinnitus/treatmnt.html#gingko
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  47. ^ Kade, F.; Miller, W. (1993). "Dose-dependent effects of Ginkgo biloba extraction on cerebral, mental and physical efficiency: a placebo controlled double blind study". British journal of clinical research 4: 97–103. 
  48. ^ a b Lovera, J; Bagert, B; Smoot, K; Morris, CD; Frank, R; Bogardus, K; Wild, K; Oken, B et al. (2007). "2006 ACTRIMS ABSTRACTS: Biomarkers in MS/Basic and clinical issues in multiple sclerosis research ACTRIMS 11th annual meeting, October 8, 2006, Chicago, Illinois". Multiple Sclerosis 13 (3): 376–85. doi:10.1177/1352458506071213. PMID 17439907. 
  49. ^ Parsad, D.; Pandhi, R.; Juneja, A. (2003). "Effectiveness of oral Ginkgo biloba in treating limited, slowly spreading vitiligo". Clinical and Experimental Dermatology 28 (3): 285–7. doi:10.1046/j.1365-2230.2003.01207.x. PMID 12780716. 
  50. ^ Jiang, Xuemin; Williams, Kenneth M.; Liauw, Winston S.; Ammit, Alaina J.; Roufogalis, Basil D.; Duke, Colin C.; Day, Richard O.; McLachlan, Andrew J. (2005). "Effect of ginkgo and ginger on the pharmacokinetics and pharmacodynamics of warfarin in healthy subjects". British Journal of Clinical Pharmacology 59 (4): 425–32. doi:10.1111/j.1365-2125.2005.02322.x. PMID 15801937. 
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  54. ^ Complete Ginkgo information from Drugs.com

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Ginkgo biloba is either extinct in the wild or drastically restricted in range. The species is reported to occur naturally in remote mountain valleys in China's Zhejiang province (C. N. Page 1990). Persistence of trees planted about dwellings, however, when no trace of the dwellings remains, complicates discerning the status of such trees. Most, if not all, ginkgoes exist only in cultivation.

In the flora area seeds of ginkgo, minus the fleshy outer coat, have been found beneath various species of trees up to 150 m from the nearest seed-producing ginkgo. The dispersal agents were almost certainly birds, possibly crows. A cache of ginkgo seeds, in association with scats of raccoons [ Procyon lotor (Linnaeus), family Procyonidae], was found in a tree crotch about 50 m from the nearest source of the seeds (J. W. Thieret, pers. comm.). Apparent animal dispersal of ginkgo requires further study.

Seedlings or saplings of ginkgo are very rarely found in the vicinity of planted trees and in fencerows and woods (undocumented reports from Kentucky, New Jersey, New York, Ohio, Pennsylvania, and Virginia), hence the inclusion of the species in the flora. Nevertheless, the species is doubtfully naturalized in North America despite about two centuries of cultivation here.

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A relict species of the Mesozoic era, this and other (extinct) species of Ginkgo were formerly widespread throughout the world. The atavistic, leaf-marginal seeds of one cultivated clone may suggest an affinity with the extinct pteridosperms. Ginkgo biloba is now a rare species in the wild, but has been widely cultivated as an ornamental, probably for more than 3000 years. It provides shade and is tolerant of a wide range of climatic and edaphic conditions, including pollution. It is sacred to Buddhists and is often planted near temples. The wood is used in furniture making, the leaves are medicinal and used for pesticides, the roots are used as a cure for leucorrhea, the seeds are edible, and the bark yields tannin.
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Names and Taxonomy

Taxonomy

Comments: The only extant species of its order, and perhaps class and even phylum. Native to China, widely cultivated, and occasionally escaped elsewhere. Considered by some (e.g., Margulis and Schwartz, 1998) to belong to the monotypic phylum (division) Ginkgophyta, by others to be a monotypic class (Ginkgoopsida) within the Gymnospermae, and by yet others (e.g., Krussmann, 1985) to be a monotypic order within the class Cycadopsida of the phylum Gymnospermae. Although sometimes appearing as 'Ginkgopsida', the correct spelling of the name at the class level is 'Ginkgoopsida', according to e-mail from Jim Reveal to Martha Martinez 14Apr97 and Larry Morse discussion 1Jun99 and e-mails 2Jun99 with Dan Nicolson, Smithsonian, adding the ending '-opsida' to the indeclinable non-Latin genus name 'Ginkgo', following the pattern of the family name 'Ginkgoaceae' (ICBN, 1994). LEM 28May99 & 2Jun99.

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