Ginkgo ovule development, pollen and video photos motile sperms

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Below you can see:

- schemes of the ovule development

-short movie scene showing two motile sperms + snapshots + YouTube video and more

ovules with pollination droplet (photo Cor Kwant)

pollination droplet is present on the micropyle
at the tip of the integument

Ovule development

Ovule development gametophyte

immature seed
immature (left) and mature (right) enlarged, fleshy seed with inner hard part (black)
Drawings adapted from Fig. 22-15 in Bold, H. C. et al. (1987), Morphology of plants and fungi, 5th ed. New York, Harper & Row.

Drawings courtesy University of Toronto (Canada).

Ginkgo embryo
young embryo
Ginkgo female ovuliferous structures
female ovuliferous structures

images University of Lethbridge, Alberta, Canada

Drawing after 'Pour la Science' 2008.

pollen
microstrobilus

Ginkgo pollen

images University of Lethbridge, Alberta, Canada

motile sperms in the pollen chamber

During the months following pollination, the pollen grows big enough to form two motile sperms in the pollen chamber.

Click here to see a short film scene (2.2 MB) showing two motile Ginkgo sperms.

Scene from the research film 'The sea in the seed, sperm of Ginkgo biloba and reproductive evolution in plants' , produced by Okada Kazuo; the best scientific film award at Ronda, Spain and TEPIA Grand Prix in Tokyo (2000) - TokyoCinema Inc.

Some snapshots from this film :


Spring: the pollen on the male Ginkgo tree are growing.	The pollen grains are released from the pollen sacs of male trees (April-May); they are carried to the female trees by the wind.	The pollen grain is four-celled. One of the cells produces sperms. A pollen grain is therefore a "flying gametophyte".	On the tip of a young ovule is a pore through which the pollen enters.

When it is ready for pollination a droplet is released from the inside of the ovule to catch the pollen.	Repeatedly the drop retracts in the tiny opening and brings the pollen grains into the pollen chamber.	Fertilization does not occur immediately after pollination. The actual fertilization mostly takes place in fall (depending on external temperature). Inside the archegonia egg cells are maturing.	Usually only one of the two fertilized eggs germinates. During the months following pollination, the pollen forms two sperms in the pollen chamber, absorbing water and fertilizer from the female tissue - a nucellus.

The pollen chamber and the space around the tentpole unite into a bigger archegonial chamber. This fluid could be regarded as "the sea" in the seed.	Two sperms in the pollen tube.	The pollen tube ruptures and the Ginkgo sperms swim upwards in "the sea" toward the eggs. The Ginkgo sperm has c. 1000 flagella (cilia) arranged in a spiral.	The sperm of the Ginkgo has many similarities with that of the Cycad. The Cycad and Ginkgo have partially followed the same reproduction method the ancestors of green plants had in the water; they produce a similar watery environment in a seed.
		More info on my Propagation-page.	Videos I made of pollen / seeds: click here. More photos of the seed development here.
Ginkgo sperms swim forward with cilia at the front. Compared to mosses and ferns, Ginkgo sperm can swim safely in this "inner sea" and can reach the egg cells more successfully.	The sperms swim shortly in the liquid. The egg cells attract nearby sperms to the entrance of the archegonium, then one of them fuses with the egg nucleus, the actual fertilization. Ginkgo biloba and the cycads are the only living seed plants with motile sperm cells.	.	.

Watch the full movie "The sea in the seed" on YouTube.

The spermatozoid of Ginkgo biloba
Video on YouTube about the spermatozoid of Ginkgo biloba, first discovered in seeds obtained by Sakugoro Hirase in 1896. More on this video: Cycas revoluta and Slime mould.
From ScienceNet, Japan

Video fragment: spermatozoid of Ginkgo biloba
(This fragment is not on YouTube; loading please wait.)
From ScienceNet, Japan

Videos I made of trees / pollen / seeds: click here.

Watch video (Japanese): Swimming Ginkgo sperm (includes micro fragments): click here.

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