100 pollen for Pollination!
How can a flower ensure that exactly one fertile sperm reach every ovule during pollination?
As we all know, pollination involves a whole 100+ pollen grains sticking onto the stigma of the flower. From there, they will all compete to grow pollen tubes down the style which are tasked with the job of delivering the male gametes to fuse with the female ones (ovules). The exact number of male and female gametes must fuse- no more, no less.
Sometimes, fertilisation fails. One reason is because of the abnormal development of pollen tubes, like venturing in the wrong direction and not reaching the ovules, swelling of the tips or coiling of the tubes. This is clear-cut, no explanation needed. Another occurs even when the male and female gametes meet- the male gamete is not working. Thus, the flower cannot accept too many, for they would be extras if the first gamete works, nor can it accept too little, as there are chances of failures.
To prevent any mishaps, the flower utilises a unique mechanism to make sure that only the minimum number of male gametes necessary reach the ovules. Brown University biologists have reported that once a successful fertilisation has occurred, the flower immediately stops signalling other pollen tubes from entering. This safeguard system guarantees that there would be seed formation without "spamming" the ovules unnecessarily. No extra pollen tubes would interfere with the fertilisation process anymore.
As we all know, pollination involves a whole 100+ pollen grains sticking onto the stigma of the flower. From there, they will all compete to grow pollen tubes down the style which are tasked with the job of delivering the male gametes to fuse with the female ones (ovules). The exact number of male and female gametes must fuse- no more, no less.
Sometimes, fertilisation fails. One reason is because of the abnormal development of pollen tubes, like venturing in the wrong direction and not reaching the ovules, swelling of the tips or coiling of the tubes. This is clear-cut, no explanation needed. Another occurs even when the male and female gametes meet- the male gamete is not working. Thus, the flower cannot accept too many, for they would be extras if the first gamete works, nor can it accept too little, as there are chances of failures.
To prevent any mishaps, the flower utilises a unique mechanism to make sure that only the minimum number of male gametes necessary reach the ovules. Brown University biologists have reported that once a successful fertilisation has occurred, the flower immediately stops signalling other pollen tubes from entering. This safeguard system guarantees that there would be seed formation without "spamming" the ovules unnecessarily. No extra pollen tubes would interfere with the fertilisation process anymore.
The procedure
Firstly, the team sent in healthy sperm through coloured tubes. It was discovered that ovules did block multiple tubes from entering the ovules.
Then, the team unleashed sperms in which a quarter of them were duds (not working; by using mutated gametes called hap2). An ovule actually attracted 4 ovules, as the first three it attracted were duds while the last was healthy. Many other ovules also attracted similar duds. This proves that signalling of pollen tubes end only when a successful fertilisation has occurred.
Nature's wondrous work of allowing only the perfect number of gametes for fusion is really astounding! This type of mechanism has greatly interested me, as I am wondering if this could happen in humans as well. For couples who do not want fraternal twins when the mother gives birth, the rate of having them decreases as the mechanism would allow only one sperm from the father to meet the mother's ovum, and not two.
Firstly, the team sent in healthy sperm through coloured tubes. It was discovered that ovules did block multiple tubes from entering the ovules.
Then, the team unleashed sperms in which a quarter of them were duds (not working; by using mutated gametes called hap2). An ovule actually attracted 4 ovules, as the first three it attracted were duds while the last was healthy. Many other ovules also attracted similar duds. This proves that signalling of pollen tubes end only when a successful fertilisation has occurred.
Nature's wondrous work of allowing only the perfect number of gametes for fusion is really astounding! This type of mechanism has greatly interested me, as I am wondering if this could happen in humans as well. For couples who do not want fraternal twins when the mother gives birth, the rate of having them decreases as the mechanism would allow only one sperm from the father to meet the mother's ovum, and not two.
Watch this animation to refine your knowledge of pollination a bit (click on it!)