Ginkgo

Ginkgo biloba is a woody tree with a spreading form and a large trunk that reaches a height between fifty to eighty feet. The trees are sexually dimorphic (two-forms), and male trees typically have steep branching angles while female trees are broadly branched. Ginkgo grows in temperate climates and is long-lived, with trees up to one thousand years old having been reported.

Ginkgo is characterized by flattened, often bilobed leaves, with numerous fine veins that lack a midvein. Leaves are clustered on slow-growing, short shoots or spaced spirally on elongated shoots. Ginkgo trees are deciduous and the silhouettes of its bare branches make it easy to identify male and female trees. The pollen of Ginkgo is called prepollen because it produces a haustorial tube upon germination and only after several months releases a motile sperm cell that swims to fertilize the egg. Ginkgo is one of the most advanced land plants still fertilized by motile sperm cells. Ginkgo is a gymnosperm that produces specially modified plumlike seeds that, even though they look like fruits, botanically are seeds. The seed is surrounded by a thin papery inner seed coat, a middle shell-like hard seed coat, and a fleshy outer seed coat that ripens to a soft, pulpy, foul-smelling mass when the seeds are dropped from the female trees.

Ginkgo biloba has a long history, with ancestors extending back some 280 million years into the Permian. It is one of very few plants living today that has such a clear lineage dating back into the Paleozoic era. During the Mesozoic era the Ginkgo lineage diversified and spread to many parts of the world. During the Cretaceous, there were seven to ten species of Ginkgo trees living, and they would have been a common sight among the dinosaurs of the Northern Hemisphere. Fossil Ginkgo leaves and petrified trunks can be found during the Tertiary period in North America, Europe, and Asia where trees lived until less than five million years ago.

There is now only one living species in the family Ginkgoaceae, a once diverse and widespread group, and it is indigenous to only a small area in China. Although nearly extinct in the wild, it has been preserved as a living fossil because it was planted at the entrances to Chinese and Japanese temples. Ginkgo has commonly been planted as a street tree in temperate North American cities (such as Washington, D.C.). Male trees are often vegetatively propagated for this purpose because they lack the foul-smelling, fleshy fruitlike seeds. Ginkgo trees are quite tolerant of city pollution.

The cleaned seeds and leaves are reported to have beneficial health effects on the brain, hearing, eyes, lungs, kidneys, liver, and general circulation. The seeds are eaten and the leaves used to prepare tea. It is used for its antibacterial effects and benefits for nerves, asthma, vision, improving blood flow, and slowing aging. Several secondary metabolites such as flavonoids , terpenoids (e.g., ginkgolides A, B, and C, bilobalide, ginkgetin, and isoginkgetin), and organic acids are some of the chemicals isolated from Ginkgo. Extracts of Ginkgo are sold as a health diet supplement.

see also Evolution of Plants; Gymnosperms; Systematics, Plant; Taxonomy; Trees.

David Dilcher

Bibliography

Hobbs, C. Ginkgo, Elixir of Youth. Loveland, CO: Botanica Press, 1991.

Hori, T., R. W. Ridge, W. Tulecke, P. Del Tredici, J. Tremouillaux-Guiller, and H. Tobe, eds. Ginkgo Biloba—A Global Treasure. Tokyo: Springer-Verlag, 1997.

Ginkgo

The ginkgo, or maidenhair tree (Ginkgo biloba ) is an unusual species of gymnosperm, having broad leaves, and seasonally deciduous foliage that turns yellow and is dropped in autumn. The ginkgo is a dioecious plant, which means that male and female functions are performed by separate trees. The ginkgo is considered a living fossil, because it is the only surviving member of the family Ginkgoaceae and the class Gingkoales. This is a group of gymnosperms

with a fossil lineage extending back to the lower Jurassic, some 190 million years ago, and once probably having a global distribution.

In more modern times, the natural distribution of the ginkgo was apparently restricted to a small area of southeastern China. It is very likely, however, that there are no longer any truly natural wild populations of ginkgo in forests in that region. It appears that the only reason this remarkable species still survives is because it was preserved and cultivated in small groves around a few Buddhist temples. This was apparently done because farsighted monks recognized the ginkgo as a unique species of tree, and because they valued its edible, possibly medicinally useful fruits and leaves. Gingko is still used in this way today, as an herbal medicine thought to be useful in the treatment of memory loss, asthma, circulatory disorders, headaches, impotence, and a variety of other ailments.

Today, the ginkgo is no longer a rare species, and it has a virtually worldwide distribution in temperate climates. It has become commonly grown in cities and gardens as a graceful and interesting shade tree. The ginkgo has attractive, golden-yellow foliage in autumn, is easy to transplant and cultivate, and is remarkably resistant to diseases, insects, and many of the stresses of urban environments including, to some degree, air pollution. The ginkgo is also often cultivated because of its special interest to botanists and others as a living fossil.

Often, horticulturists attempt to plant only male ginkgos, because the outer flesh of the fruits of female trees can have an uncomfortably foul odor, making some people nauseous, and causing skin rashes upon contact. Ginkgo trees can reach a height of about 115 feet (35 m), and can achieve a trunk diameter of more than 27 inches (68.5 cm). Trees mature at about 20 years, and can live to be older than 1,000 years.

Ginkgo

The ginkgo, or maidenhair tree (Ginkgo biloba) is an unusual species of gymnosperm , having broad leaves, and seasonally deciduous foliage that turns yellow and is dropped in autumn. The ginkgo is a dioecious plant , which means that male and female functions are performed by separate trees. The ginkgo is famous as a socalled "living fossil," because it is the only surviving member of the family Ginkgoaceae and the class Gingkoales. This is a group of gymnosperms with a fossil lineage extending back to the lower Jurassic, some 190 million years ago, and once probably having a global distribution.

In more modern times, the natural distribution of the ginkgo was apparently restricted to a small area of southeastern China. It is very likely, however, that there are no longer any truly natural, wild populations of ginkgo in forests in that region. It appears that the only reason this remarkable species still survives is because it was preserved and cultivated in small groves around a few Buddhist temples. This was apparently done because farsighted monks recognized the ginkgo as a special, unique species of tree, and because they valued its edible, possibly medicinally useful fruits and leaves. Gingko is still being used in this way today, as a "herbal" or "folk" medicine thought to be useful in the treatment of memory loss, asthma , circulatory disorders, headaches, impotence, and a variety of other ailments.

Today, the ginkgo is no longer a rare species, and it has a virtually worldwide distribution in temperate climates. This is because the ginkgo has become commonly grown in cities and gardens as a graceful and interesting shade tree. The ginkgo has attractive, golden-yellow foliage in autumn, is easy to transplant and cultivate, and is remarkably resistant to diseases, insects , and many of the stresses of urban environments including, to some degree, air pollution . The ginkgo is also often cultivated because of its special interest to botanists and others as a living fossil.

Often, an attempt is made by horticulturists to only plant male ginkgos, because the outer flesh of the fruits
of female trees can have an uncomfortably foul odor, making some people nauseous, and causing skin rashes upon contact. Ginkgo trees can reach an height of about 115 ft (35 m), and can achieve a trunk diameter of more than 27 in (68.5 cm). Trees mature at about 20 years, and can live to be older than 1,000 years.

Ginkgo A genus whose sole living member, G. biloba, is the maidenhair tree, native in China. It is deciduous, has leaves with open dichotomous venation, and is dioecious. The naked seed is oily and edible but the testa and embryo are bitter. It is widely cultivated. Many fossil species are known. G. digitata, the earliest representative of the genus, is first recorded from the Middle Jurassic and bears a close resemblance to its living relative. See GINKGOPHYTA.

gink·go / ˈgingkō/ (also gingko) • n. (pl. -oes or -os) a deciduous Chinese tree (Ginkgo biloba, family Ginkgoaceae) related to the conifers, with fan-shaped leaves and yellow flowers.