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Ginkgo

From Academic Kids

Ginkgo
Conservation status: Endangered
Missing image
Gingko-Blaetter.jpg



Ginkgo leaf
Scientific classification
Kingdom:Plantae
Division:Ginkgophyta
Class:Ginkgoopsida
Order:Ginkgoales
Family:Ginkgoaceae
Genus:Ginkgo
Species:G. biloba

Template:Taxobox section binomial botany

The Ginkgo (Ginkgo biloba), sometimes also known as the Maidenhair tree, is a unique tree with no living relatives. It is classified in its own division, the Ginkgophyta, comprising the single class Ginkgoopsida, order Ginkgoales, family Ginkgoaceae, genus Ginkgo and just the one species. It is one of the best examples of a living fossil known. In the past it has also been placed in the divisions Spermatophyta or Pinophyta. Ginkgo is a gymnosperm (as opposed to an angiosperm), meaning "naked seed"; its seed embryos are not protected by a seed shell at pollination, but are exposed to the air.

For centuries it was thought to be extinct in the wild, but is now known to grow wild in at least two small areas in Zhejiang province in eastern China.

Contents

Characteristics

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Ginkgo_biloba0.jpg
Ginkgo fruit and leaves

The Ginkgo is a medium-large deciduous tree, reaching 20-35 m tall, with an often angular crown with long, somewhat erratic branches. They are very long-lived, with some specimens thought to be more than 2,500 years old.

The leaves are unique among seed-bearing plants, being fan-shaped with veins radiating out with the leaf blade, sometimes bifurcating but never anastomosing (branching); they are 5-15 cm long. The old popular name "Maidenhair tree" is because the leaves resemble some of the pinnae of the Maidenhair fern Adiantum capillus-veneris. Sometimes leaves are notched or lobed, but only from the outer surface, between the veins. The leaves are borne both on the more rapidly-growing branch tips, where they are alternate and spaced out, and also on short, stubby spur shoots, where they are clustered at the tips.

The seed is 1.5-2 cm long and contained inside a light yellow-brown coloured, soft fruit-like coating 2-3 cm in diameter. It is plum-like and attractive, but contains butanoic acid and thus smells like rancid butter (which contains the same chemical).

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Gingko_biloba3.jpg
Ginkgo ripe fruit and autumn leaf colour

Gingkos are dioecious, with separate sexes, some trees being female and others being male. In some areas, most trees planted are male stock grafted onto roots propagated from seed, because the male trees will not produce the fleshy, smelly, ovaries.

The name Ginkgo means "silver apricot" (銀杏 yn xng) in Chinese. The same name was used in Japan (where Ginkgo had been introduced from China) in the 17th century, but the Japanese pronunciation was ginkyō. This was the name encountered by Engelbert Kaempfer, the first Westerner to see the species, in 1690. The modern Japanese reading is ichō or ginnan (although the kanji text is the same). The modern Chinese name is 白果 (bái guǒ), meaning "white fruit".

Prehistory

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Fossil_Plant_Ginkgo.jpg
Fossil Ginkgo leaves from the Jurassic of England

The Ginkgo is a living fossil, with fossils recognisably related to modern Ginkgo from the Permian, dating back 270 million years. They spread and diversified throughout Laurasia during the middle Jurassic and Cretaceous, but became much rarer thereafter. By the Paleocene, Ginkgo adiantoides was the only Ginkgo species left, and at the end of the Pliocene Ginkgo fossils disappeared from fossil record everywhere apart from a small area of central China where the modern species survived.

Ginkgophyta fossils have been classified in the following families and genera:

  • Ginkgoaceae
    • Arctobaiera
    • Baiera
    • Eretmophyllum
    • Ginkgo
    • Ginkgoites
    • Sphenobaiera
    • Windwardia
  • Trichopityaceae
    • Trichopitys

Ginkgo has been used for classifying plants with leaves that have more than four veins per segment, while Baiera for those with less 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

It 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 coming across it is in 1690 in Japanese temple gardens. Because of its status in Buddhism and Confucianism, the Ginkgo is also widely planted in Korea and parts of Japan; in both areas, some naturalisation has occurred, with Ginkgos seeding into natural forests.

The seed is edible after removing the ovary pulp, shelling, and after being cooked. Usually only a few are added for a portion enough for ten people. An overdose of the fruit would cause poisoning because the fruit produces hydrogen cyanide as a side product. It is known that a dozen raw ginkgo fruits are toxic enough to kill a small child.

Some people are sensitive to the chemicals in the ovary pulp, and if sensitive, the seeds should be handled with care when cleaning, wearing disposable gloves. The symptoms are a rash or blisters similar to that from poison-ivy.

The seed are a traditional Chinese food, e.g. congee, often served at weddings, and sometimes believed to have health benefits; some also consider them to have aphrodisiac qualities, although this has yet to be proved. Japanese cooks add Ginkgo seeds to dishes such as chawammushi.

Ginkgo as penjing in the Montreal Botanical Gardens
Enlarge
Ginkgo as penjing in the Montreal Botanical Gardens

The Ginkgo has the intriguing distinction of being one of the world's most urban-tolerant trees, often growing where other trees cannot survive. Some claim that only one tree, the Tree-of-heaven, is more urban-tolerant. This makes it all the more puzzling why all of its relatives died out. For this reason, and for their general beauty, they are excellent urban trees. The trees are easy to propagate from seed.

Ginkgos are also popular subjects for growing as penjing and bonsai; they can be kept artificially small and tended over centuries.

Extreme examples of the Ginkgo's tenacity may be seen in Hiroshima, Japan, where four 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 & details (http://www.xs4all.nl/~kwanten/hiroshima.htm)).

Medical uses

Extracts from the Ginkgo leaves contain flavonoid glycosides, among others, ginkgolides and are therefore used as a pharmaceutical. The extract has many properties but it is mainly used as memory enhancer and anti-vertigo agents. However, studies differ about its efficacy.

Throughout the past three decades, more than 300 studies have shown Ginkgo that provides a number of benefits. The most important are listed below.

  • Increases blood flow to the brain and throughout the body's blood vessels that provide blood and oxygen to the organ systems
  • Increases metabolism efficiency, regulates neurotransmitters, and oxygen levels in the brain
  • Enhanced circulation in the brain include improved short and long term memory, reaction time and mental clarity
  • Helps control the transformation of cholesterol to plaque associated with the hardening of arteries, and may relax constricted blood vessels
  • Ginkgo has been shown to be a supportive herb for treating infertility or impotence in males
  • Aids in preventing damage to organs from free radicals, and also blocks the platelet activating factor which causes some skin disorders such as psoriasis
  • Helps in the treatment of eye and ear disorders
  • Recent studies have shown that Ginkgo helps reduce altitude sickness.

Side effects

Like all things, Ginkgo may have some undesirable effects, especially for individuals with blood circulation disorders and those taking anti-coagulants such as aspirin. It should also not be used by people who are taking the anti-depressant drugs known as monoamine oxidase inhibitors (MAOI) or pregnant women.

Below are some Ginkgo side effects and cautions:

  • gastrointestinal discomfort
  • headaches
  • may increase risk of bleeding, and should not be used if you have a clotting disorder
  • Ginkgo should not be used by pregnant women
  • restlessness
  • diarrhea
  • nausea
  • vomiting

If any side effects are experienced the dosage should be lowered immediately. Ginkgo supplements are usually taken in the range of 40 mg to 200 mg per day. If the side effects continue usage should be stopped completely.

External links

Template:Commonscs:Jinan dvoulaločn da:Tempeltr (Ginkgo biloba) de:Ginkgo es:Ginkgo sv:Ginkgo eo:Ginko fr:Ginkgo biloba he:גינקגו דו אונתי it:Ginkgo biloba nl:Ginkgo biloba ja:イチョウ pl:Miłorząb dwuklapowy pt:Ginkgo zh:银杏

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