Gung-ho for ginkgo The ginkgo or “maidenhair tree” (Ginkgo biloba) is the one of the oldest living tree species and sole survivor of the order Gingkoales. It has survived relatively unchanged for millions of years as the two pictures attest: the first image is of a modern-day leaf, while the second dates back to the Eocene (55-33.9 mya). This longevity is attributed to it’s long-livedness (a single tree may live up to 1,000 years) and slow reproduction rate, taking 40 years to reach maturity. A wide, contiguous distribution is reflected in the fossil record, as well as by virtue of their nature as tough, hardy plants which are resistant to pests and pollution. Ginkgoes are known for their distinctive, fan-shaped, leaves. The species name “biloba” refers to the deep notch that gives a double-lobed appearance, and their similarity to the leaves of the maidenhair fern are reflected in their other common name. However, a single tree may produce several different leaf shapes, making it challenging for palaeobotanists to determine species diversity from fossil leaves. The gingkos ancient cousins date back to the Permian (270 mya) with the genus reaching maximum species diversity during the Cretaceous (145-66 mya). The other members of Ginkgoales died out during the Pliocene (5.33-2.58 mya) and their once worldwide distribution was reduced to a single species found only in small area of central China. Today, it is been cultivated all over the world and is considered a sacred tree by Buddhist monks. A recent (2013) molecular phylogenetic study concluded that Ginkgophyta (ginkoes) are monophyletic with Cycadophyta (cycads) - that is, they share a common ancestor from which they both diverged as two of the oldest divisions of gymnosperm; non-flowering plants that produce ‘exposed’ seeds on leaves or scales (of which cones are a modified form). Previously, their closest relative was considered to be the Coniferophyta (conifers). Here is an introduction to the four divisions (the botanical equivalent of phyla) of gymnosperms: bit.ly/1wAe29t. It is thought that Ginkgoales arose from the seed ferns (Pteridospermatophyta, specifically order Peltaspermales) although this is yet to be confirmed by palaeobotanists. Ginkgo biloba leaves and seeds are well known as both traditional Chinese and western medicinal herbs, although western medicine has only focused on an extract derived from the dried leaves. The plant contains over 40 components, however only two are pharmaceutically useful - the flavonoids and terpenoids. Clinical studies suggest that these extracts may be useful in treating blood disorders, vision issues, and anxiety, showing positive results when compared with the placebo groups. However, the effects of ginkgo on memory function have shown mixed results. - YK Image credits: Living Ginkgo biloba - Public domain image (bit.ly/1zY6eiG) Fossil Ginkgo biloba - Public domain image (bit.ly/1FwTTdS) Further reading: Fantastic interview on ginkgoes Yale University did with botanist Peter Crane: bit.ly/1BRYMby A very comprehensive encyclopaedia article about the Ginkophytes: bit.ly/1tRNFAq The molecular phylogenetic study: bit.ly/1yHtXbA Medicinal information on Ginkgo biloba: bit.ly/1KqTdXn Dear Readers, Most of our posts are not reaching your news feed due to fbs filtering system. If you wish to enjoy our posts more often, use the following for information on how to go about it: tmblr.co/Zyv2Js1VWMUJ0.
Posted on: Sat, 10 Jan 2015 06:12:01 +0000
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