Smallest Gametophyte?

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Navin
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Smallest Gametophyte?

Post by Navin » Tue Feb 27, 2007 3:11 pm

I have learnt that a characteristic in spermatophytes (the seed plants) is a "reduced gametophyte". The male gametophyte is basically found in the germinating pollen grain, whilst the female gametophyte is found in a mature ovule.

My question is, generally speaking, where would I find the smallest gametophyte? Is it in gymnosperms or angiosperms?

My answer would be gymnosperms - mainly because the female gametophyte in angiosperms consists of 7-8 cells, whilst the female gametophyte in gymnosperms contain only 2-4 eggs.
Is my reasoning accurate or have I missed out some important facts?

Thanks in advance.
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Post by SU_reptile » Tue Feb 27, 2007 8:16 pm

the female gametophyte in gymnosperms contain only 2-4 eggs.

That's not true. Female gametophyte in Gymnosperms (better name is Pinophyta) contains lots of cells and those 2-4 egg cells. Egg cells with their ventral canal cells and neck cells form archegonia.
That female gametophyte or female prothallus arises by means of number of divisions done by the megaspore and only 2-4(5) turn into egg-cells.
If you're interested in sexual reproduction i strongly recommend reading something about Gnetophytina (for example Gnetum gnemon). They have a peculiar way of creating megagametophyte and they have laso something similar to double fertilization occuring in Magnoliophyta.

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Post by Navin » Wed Feb 28, 2007 2:38 am

ah, ok.

So i guess by means of evolution of the reduced gametophyte, then I can say that the angiosperms have the smallest gametophyte.
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Post by SU_reptile » Wed Feb 28, 2007 3:39 pm

Among vascular plants - yes. But I am not sure whether some algae have smaller gametophytes. I shall check it. You see, there are some algae that have heteromorphic generation alternation with gametophyte that is smaller than sporophyte. Then gametophyte is usually comprised of a few cells only.

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