- August 28, 2005 at 6:34 pm #1762EdherParticipant
At this moment, I’m studying the reproductive cycle of angiosperms.
My question is, when pollen grains are transferred from anthers of stamen to the stigma of carpel, how many pollen grains actually enter the carpel?
What happens when one pollen grain has already developed its respective tube?
Does that take up the girth of the style and prevent from other entering pollen grains to develope their tubes?
Furthermore, what happens when a pollen grain developes a tube that reaches an ovule that has already been fertilized?
- August 28, 2005 at 9:42 pm #28968ERSParticipant
The number of useful pollen grains that enter the carpel depends on what type of angiosperm you are dealing with. If it has multiple archegonia, then several pollen grains may be required.
Pollen grains contain chemicals that may react with chemicals in the stigma of the flower. Depending on the reactions, the pollen grain may germinate and begin developing a pollen tube or not. This chemical signaling also aids foreign pollen grains from entering the carpel.
If a pollen grain shows up at the ovule doorstep to find it is not needed, then it will generally just dissolve into the surrounding plant tissues. If it even gets there, that is, remember much of biology is chemistry.
The pollen tube itself is not very big, remember the sperm nuclei may have a long way to travel and time may be of the essence, therefore excessive girth is a waste of time.
did this answer your question, or just further muddy the water?
anyone else want to add?
- August 29, 2005 at 6:12 pm #28992MrMisteryParticipantquote Edher:
Nothing 😀 It is like having sexual relations with a woman who is already pregnant 😉
- August 30, 2005 at 4:34 pm #29037PoisonParticipantquote MrMistery:
Great example, Andrew. 😀 😀
- August 31, 2005 at 8:30 pm #29064MrMisteryParticipant
I find it very easy to understand basic biology using analogies to day-to-day life. And that is pretty much as day-to-day as it can get 😀
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