Difference between revisions of "Ginkgo"
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Revision as of 22:54, 13 December 2009
The Ginkgo is a unique tree with no close living relatives. The only known living species classified as Ginkgo biloba has been assigned it own taxonomic division of Ginkgophyta. It is a living fossil remaining essentially unchanged since creation. For centuries people thought this group of trees was extinct in the wild, but now it is found to grow around the Zhejiang province in eastern China and in the Tian Mu Shan Reserve.
The Ginkgo trees leaves are fan shaped and flat with irregular notches in them. They also have grooves in the middle of the leaf producing two distinct lobes. The leaves grow in clumps on the tips of short shoots that can be up to 3 inches long. The ginkgo has a vascular system and the bark is often a grey color, yet on the inside it is yellow. In autumn the leaves turn a golden brown.
Ginkgos are dioecious, meaning they are found with two separate sexes (either female or male). They are also gymnosperms meaning, "naked seed." Unlike angiosperms it is the seeds that are not protected by an ovary wall. Therefore the berry-like structures produced by female ginkgo trees are technically not fruit.
Male plants produce pollen cones with sporophylls. Female plants don't produce cones. Two ovules are formed at the end of a stalk, and after pollination one or both develop into seeds. The seeds are about 1.5-2 cm long and are a light yellowish-brown color. The Gingkos are odd in the fact that they use motile sperm. When the pollen in the Ginkgos reaches the pollen chamber it has two sperms that are produced, one of them is used to fertilize the ovule.
The Ginkgo is found to grow in the wild around the Zhejiang province in eastern China and in the Tian Mu Shan Reserve. It has been cultivated in China for centuries. In fact, some planted trees at temples are believed to be over 1,500 years old. Because of its status in the religions of Buddhism and Confucianism, the Ginkgo is also widely planted in Korea and parts of Japan where it has spread into natural forests.
The extract of the Ginkgo leaves has been used in pharmaceutics as a memory enhancer and anti-vertigo agent. Recent studies have also indicated that Ginkgo shows promise in the treatment of Alzheimer's disease.
- Main Article: Living Fossils
The Ginkgo is a living fossil. Living fossils are plants or animals that closely resemble species known from fossils. Many living fossils were considered extinct and only known through fossil evidence, but were later discovered to still be alive in Japanese temple gardens around 1691. The Ginkgo exists essentially unchanged from relatives supposedly dating back some 270 million years by radiometric dating techniques and evolutionary assumptions.