ANA SAYFA


POLLEN GRAIN AND EMBRYO SAC DEVELOPMENT
 
 
 
Flower structure:
 
 
 
 
 
 
*Pollen grain development:
 
→Flowering plants produce pollen grains, within the male reproductive organ which is called stamen.
 
→The pollen grain develops within the microsporangia, at the tips of the stamen which is called anther.
 
→Each of the microsporangia, contains microsporocyte which is called microspore mother cell.
 
 
 
 
→Microsporocyte undergoes meiosis that produce four haploid microspores.
 
→Then, nucleus of the microspore; undergoes mitosis and thus, the pollen grain which has two nuclei form.
 
 
 
The pollen grain structure:
 
 
→Within the pollen grain: there are two nuclei that comprise the male gametophyte.
 
→One of them is the tube nucleus which develops into the pollen tube, after pollination.
 
→The other one is the generative nucleus which undergoes mitosis to produce two sperm cells, after pollination.
 
 
 
 
*Embryo sac development:
 
→Flowering plants produce embryo sac, within the female reproductive organ which is called carpel.
 
→The embryo sac develops, within the megasporangium, at base of the carpel which is enclosed by ovary.
 
→Each of the megasporangium, contains megasporocyte which is called megaspore mother cell.
 
 
 
 
→Megasporocyte undergoes meiosis that produce four haploid cells.
 
→Three of the cells degenerate and only one of them stays alive which is called megaspore.
 
 
→Then, megaspore grows and its nucleus undergoes three mitosis.
 
→Thus, the embryo sac which has eight nuclei form.
 
 
 
The embryo sac structure:
 

 

 
 
 
 
 
 
 
 
 
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