A) 1-celled stage
B) 2-3- celled stage
C) 4- celled stage
D) 5- celled stage
Correct Answer: B
Solution :
Pollen grain protoplast is uninucleate (1 celled) in the beginning but at the time of liberation it becomes 2-3 celled. Actually, pollen grain nucleus grows in size and shifts to one side near the wall. The protoplast then divides to form two unequal cells-generative cell (small) and tube or vegetative cell (large). In some species, the generative cell divides into two male gametes prior to the dehiscence of anther and release of the pollen grains. Thus, at the time of pollination, pollen grain is either 2-celled (tube cell + generative cell) or 3-celled (tube cell 4- two male gametes). Pollen grains has not been noted so far in 4-celled and 5-celled stage.
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