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Double Fertilization

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Double Fertilization

Postby martixell » Mon Apr 18, 2005 5:35 pm

If any could help me on how to explain the hypothesis of double fertilization?
:D :arrow:
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Postby Poison » Mon Apr 18, 2005 8:31 pm

what do you mean by saying "double fertilization hypothesis"?
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Re: Help!!! Double Fertilization

Postby martixell » Mon Apr 18, 2005 8:59 pm

martixell wrote:If any could help me on how to explain the hypothesis of double fertilization?
:D :arrow:
The process of double fertilization in flowering plants!! :lol:
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Postby Poison » Mon Apr 18, 2005 9:15 pm

OK. but I don't think it is a hypothesis. :)
whatever, this can be the answer of your question. (I didn't write it myself to avoid any misunderstanding. but I read it and in my opinion, it explains the process well )

Double fertilization occurs in flowering plants (angiosperms) and a few
gymnosperms (genus Ephedra and genus Gnetum). The pollen tube contains two
haploid (1n) sperm. In angiosperms, one sperm fuses with or fertilizes an egg
to produce a diploid (2n) zygote, which then divides repeatedly by mitosis and
develops into the embryo of the seed. The second sperm fuses with two, usually
haploid, polar nuclei to form a triploid (3n) nucleus termed the primary
endosperm nucleus. Both sperm fuse or "fertilize" so it is called double
fertilization. In some species the endosperm nucleus may be 2n, 5n, 9n or 15n.
For example, in lily, one of the polar nuclei is 3n so the endosperm is 5n.

The primary endosperm nucleus divides repeatedly and becomes the endosperm, a
nutritive tissue for the angiosperm embryo. The endosperm is usually cellular
but is noncellular in early stages of some species. Coconut "milk" represents
a noncellular endosperm. In some seeds, termed exalbuminous, (e.g. bean,
peanut, buckeye, chestnut, walnut, oak) the endosperm is absorbed by the
cotyledons so there is no endosperm in the mature seed. Other seeds, termed
albuminous, (e.g. corn, wheat, rice, onion, coconut, pawpaw, redbud, dogwood,
magnolia) have substantial endosperm in the mature seed. A large percentage of
the calories in the human diet come from endosperm (corn, wheat, rice, oats
and other grains). In a minority of species, notably the Orchid Family, the
endosperm does not develop or degenerates early in development.

Most gymnosperm seeds (e.g. pine, spruce, fir, ginkgo) have a haploid (1n)
nutritive tissue derived from the female gametophyte. Sometimes the gymnosperm
nutritive tissue is also called endosperm. However, it is preferred to reserve
the term endosperm for angiosperm seeds. Double fertilization in the
gymnosperm genera Gnetum and Ephedra differs from the angiosperm pattern. Two
diploid embryos are produced by double fertilization in Gnetum and Ephedra.

We are not positive why double fertilization occurs. Arthur Cronquist (1971)
considered double fertilization a "mere evolutionary happenstance." One
possible advantage of double fertilization is that the plant does not invest
energy in seed nutritive tissue until after an egg has been fertilized.
Another possible advantage is that the endosperm nucleus is very active and
divides rapidly. It forms the nutritive tissue very quickly. Rapid seed
development has obvious advantages.

Gymnosperms lacking double fertilization dominate large areas of the Earth,
e.g. the Taiga or Northern Coniferous Forest. Therefore, double fertilization
is not a requirement for success in seed plants.

Taken from: http://www.madsci.org/posts/archives/20 ... .Bt.r.html

and have a look at this too (if you are too lazy to read.. ;) )

http://www.emunix.emich.edu/~ghannan/sy ... ation.html
Last edited by Poison on Mon Apr 18, 2005 9:21 pm, edited 1 time in total.
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Postby martixell » Mon Apr 18, 2005 9:21 pm

Thank you so much, I didn't know how to put it into words. You must be really good at this stuff. :wink:
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Postby Poison » Mon Apr 18, 2005 9:22 pm

I just added something to the post. an animation. don't skip that... :)
Thank you... There are people better than me in this forum... ;)
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Postby martixell » Mon Apr 18, 2005 9:29 pm

I saw the explanation on that mini-movie, and it was the best,, it was easy to understad. How did you find that information?? :shock:
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Postby Chris4 » Tue Apr 19, 2005 11:18 am

Google search. Sorry i should let poison answer, but if you search for double fertilization on google, the animation is half way down the first page.
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Postby Poison » Tue Apr 19, 2005 3:04 pm

Oh you've found my secret!!!! :P
Just kidding of course. Chris4 is right. A google search is usually the best way to give a link. But if you are giving a link, I highly reccommend you to read the things at first. or you can give wrong info. you know, some sites are complete rubbish... :)
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Postby James » Tue Apr 19, 2005 3:11 pm

Poison wrote:Oh you've found my secret!!!! :P
Just kidding of course. Chris4 is right. A google search is usually the best way to give a link. But if you are giving a link, I highly reccommend you to read the things at first. or you can give wrong info. you know, some sites are complete rubbish... :)


Yes, 'googling' is a difficult to master art :D
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Postby Poison » Tue Apr 19, 2005 3:18 pm

I didn't mean that. I'm coming across with a lot of wrong info when I goggle. :)
But I must admit that I was lucky this time... ;)
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Postby clarence » Thu May 19, 2005 12:18 pm

I suggest you visit those sites that have the ending .edu in their addresses for some scholarly integrity. Or if the site doesn't have a specific affiliation, check for the credentials of the author who wrote the article.
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