A deciduous gymnosperm (Ginkgo biloba) originally from SW China, but probably no longer existing in the wild; leaves fan-shaped; seed with a fleshy aril covering the edible kernel; also called maidenhair tree. It is the sole living survivor of a formerly large and widespread family. (Family: Ginkgoaceae.)
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iGinkgo Conservation status: Endangered |
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Ginkgo leaf |
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Ginkgo biloba L. |
The Ginkgo (Ginkgo biloba), frequently misspelled as "Gingko", and sometimes known as the Maidenhair Tree, is a unique tree with no close living relatives. Ginkgo is a gymnosperm (as opposed to an angiosperm), meaning "naked seed"; its seeds are not protected by an ovary wall and hence, the berry-like structures produced by female ginkgo trees are technically not fruit.
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, in the Tian Mu Shan Reserve. However, as this area has known human activity for over a thousand years, the wild status of ginkgos there is uncertain.
Characteristics
Habit
Ginkgos are medium-large deciduous trees, reaching 20–35 m tall (some specimens in China being over 50 m), with an often angular crown and long, somewhat erratic branches. A combination of amazing disease resistance, insect-resistant wood and the ability to form aerial roots and sprouts means that ginkgos are very long-lived, with some specimens claimed to be more than 2,500 years old; a 3,000 year-old ginkgo is reported in Shandong province in China (Lewington and Parker, 183).
Some old Ginkgos produce aerial roots, known as chichi (Japanese;
Stem
Ginkgo branches grow in length by growth of shoots with regularly spaced leaves, as seen on most trees. In Ginkgos, as in other plants that possess them, short shoots allow the formation of new leaves in the older parts of the crown.
Leaves
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.
Leaves of long shoots are usually notched or lobed, but only from the outer surface, between the veins.
Reproduction
Ginkgos are dioecious, with separate sexes, some trees being female and others being male.
Female plants do not produce cones.
The fertilization of ginkgo seeds is by motile sperm; Although it is widely held that fertilization of ginkgo seeds occurs just before or after they fall in early autumn, embryos ordinarily occur in seeds just before and after they drop from the tree.
Name
The name ginkgo means "silver apricot" (銀杏, pinyin: yínxìng) in Chinese. The same characters are used in Japanese and Korean (where the ginkgo had been introduced from China).
In modern Japanese, the characters are read either ichō (meaning the tree) or ginnan (meaning the seed);
Prehistory
The Ginkgo is a living fossil, with fossils recognisably related to modern Ginkgo from the Permian, dating back 270 million years. By the Paleocene, Ginkgo adiantoides was the only Ginkgo species left in the Northern Hemisphere (but see below) with a markedly different (but not well-documented) form persisting in the Southern Hemisphere, and at the end of the Pliocene Ginkgo fossils disappeared from the fossil record everywhere apart from a small area of central China where the modern species survived.
At least morphologically, G. 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.
Ginkgophyta fossils have been classified in the following families and genera:
Ginkgoaceae Arctobaiera Baiera Eretmophyllum Ginkgo Ginkgoites Sphenobaiera Windwardia Trichopityaceae TrichopitysGinkgo 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.
Cultivation and uses
Ginkgo has long been cultivated in China; 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, notably the United States, most intentionally-planted Ginkgos are male cultivars grafted onto plants propagated from seed, because the male trees will not produce the malodorous seeds.
The Ginkgo has the intriguing distinction of being one of the world's most urban-tolerant trees, often growing where other trees cannot survive. Ginkgos rarely suffer disease problems, even in urban conditions, and are attacked by few insects. For this reason, and for their general beauty, ginkgos are excellent urban and shade trees, and are widely planted along many streets. The ginkgo is the official tree of the city of Kumamoto, and two leaves form the symbol of the University of Tokyo, the main campus of which is famous for its numerous ginkgos.
Ginkgos are also popular subjects for growing as penjing and bonsai;
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 & While almost all other plants (and animals) in the area were destroyed, the ginkgos, though charred, survived and were healthy.
Culinary use
The nut-like gametophytes inside the seeds are esteemed in and outside of Asia, and are a traditional Chinese food (e.g. Japanese cooks add Ginkgo seeds to dishes such as chawanmushi, and cooked seeds are often eaten along with other dishes.
When eaten by children, in large quantities (over 5 seeds a day), or over a long period of time, the raw gametophyte (meat) of the seed can cause poisoning by MPN (4-methoxypyridoxine).
Some people are sensitive to the chemicals in the sarcotesta, the outer fleshy coating.
Medical uses
The extract of the Ginkgo leaves contains flavonoid glycosides and ginkgolides and has been used pharmaceutically.
Out of the many conflicting research results, there seem to be basically three effects of Ginkgo extract on the human body: it improves blood flow (including microcirculation in small capillaries) to most tissues and organs; Ginkgo can be used for intermittent claudication.
A 2004 conference paper summarises how various trials indicate that Ginkgo shows promise in the treatment of Alzheimer's disease, although further study is needed.
Ginkgo is commonly added to energy drinks, but the amount is typically so low it does not produce a noticeable effect, except perhaps via a placebo effect from Ginkgo being listed on the label.
Side effects
Ginkgo may have some undesirable effects, especially for individuals with blood circulation disorders and those taking anti-coagulants such as aspirin and warfarin, although recent studies have found that ginkgo has little or no effect on the anticoagulant properties or pharmacodynamics of warfarin. Ginkgo should also not be used by people who are taking monoamine oxidase inhibitors (MAOI) 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, and restlessness.
If any side effects are experienced consumption should be halted immediately. Ginkgo supplements are usually taken in the range of 40–200 mg per day.
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