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GINKGO BILOBA: Reproduction  

 

Ginkgo trees, like some conifers and cycads, are dioecious, producing pollen and seeds on separate trees.  It is difficult to differentiate the sexes of the young individuals, it is necessary to wait the first flowering (not before 40 years!). Both pollen cones and seed structures grow from the spur shoots, among the leaves. Each pollen cone bears several pollen sacs. The pollen is transported by wind and produces motile sperm, not seen in the later-evolving conifers and angiosperms. The japan botanist Hirase 1856-1925) observed motile spermatozoids for the first time in the Botanical Garden of Tokyo University on September 9, 1896.

 The pollen cones appear in the early spring, while ovules appear in the fall and are shed with the leaves. The pseudo- fruits resemble small plums when ripe. They are about Ż inch in diameter. They contain a large, smooth, silvery-white seed in the center. When the fruits begin to decay after they've fallen, they emit an unpleasant odor. The Ginkgo nuts can be roasted; they are valued by the Oriental people. 

 

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BOTANICAL EXPLANATIONS

  Ginkgo disseminates neither spores (like the ferns), nor seeds (like the graminaceous ones) but something intermediary: the ovule. The ovule is the whole of the female reproductive cells i.e. the oosphere (haploid) and is additional (nucellus) They are large ovules, stuffed substances of reserve, that Ginkgo drops on the ground rather tardily in season. With the higher pole of the ovule is constituted a mini cavity filled with liquid: the pollinic room. This room presents a tiny opening, the micropyle, which produces a viscous droplet  to trap a grain of pollen if it is presented and the micropyle is closed then. Finally pollen germinates then and produces  true spermatozo´des which swim towards the female cell and penetrate to amalgamate with it.

  

Male Flowers

Female Flowers

Désolé mais votre navigateur ne supporte pas le java.

Désolé mais votre navigateur ne supporte pas le java.

The male flowers are yellowish catkins in long clusters at the end of the side boughs.

The female flowers are bare, grouped per pairs, lengthily pedunculate equipped with two free ovules

 


The fruits are often produced in great abundance and becoming an abscissing mushy mess in October, covering the ground with fleshy, strongly malodorous fruits. They then release a very nauseous odor, of a type of rancid butter, due to the presence of butyric acid. Moreover, as they are viscous, the presence of a great quantity of ovules on the roadway or on a pavement can be at the origin of accidents. Finally this pulp contains irritating and allergic substances for certain people; its handling starts  cutaneous pruriginous injuries. In fact, urban landscapers recommend only the male tree. 

Whether there is fecundation of the spermatozo´de with the oosphere  or not, the ovules enlarge and accumulate their reserves. It is a great wasting of energy for a result which can be very poor if, after a very cold time, this fecundation is not carried out.  The development is continuous and in the event of hostile environment, the seed will not be able to wait until the conditions improve. The transformation in seeds of plants with "ovules" is not effective.


    Food and Cooking 

        Ginkgo nuts have long been regarded as a delicious food by Japanese people, and these have been cooked and served in various ways depending on the time. Ginnan is the Japanese word for those seeds. Ginnan appear as a fruit or as tea cake in a textbook called Matsuya Kaiki (1533-1596), which is a series of records of tea ceremonies.

    In the Edo period, Ginkgo nuts came to be eaten by the common people. They are often regarded as a side dish when drinking sake. The most common ways of preparing Ginkgo nuts today are grilling them or boiling them in chawan-mushi ( recipe on www.kamada.co.jp ), a pot-steamed egg dish. 

Furthermore, grilled nuts are still often eaten by the Japanese today when they drink sake. More recipes on the japanese Web: Mashed Taro with Ginkgo on www.nicemeal.com/dessert, Chicken-ginnan on www.city.kyoto.jp/koho.

When seeds have been taken to excess during food shortages, Ginnan food poisoning  has sometimes occured in Japan. Ginnan food poisoning is caused by MPN (4-O-methylpyridoxine) that bas an antivitamin B6 activity. The symptoms of this poisoning are mainly convulsions and loss of consciousness. However, children are most susceptible to this type of food poisoning, and it is recommanded that consumption of Ginkgo seeds be limited to not more than five for children under 6 years. Ginkgo nuts nutriment content on nutrition.about.com.

 

Data Base on Food Poisoning by Ginkgo Seeds : www.hoku-iryo-u.ac.jp/ginkgotox.html

Data Base on Mechanism of Ginkgo Food Poisoning: www.hoku-iryo-u.ac.jp/ginkgomecha.html

 

 

  More informations about Ginkgo tree....

101 Ginkgo biloba Ginkgo Extract Where to see ?
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