Question

Why fertilisation cannot take place in flowers if pollination does not take place?

Answer 1

Because plants can only reproduce by the methods of pollination ( i.e. self and cross pollination ).
Pollination helps flowers to transfer pollen grains ( male gamete) from anther to stigma after that the fusion of male gamete with the female gamete takes place.

Answer 2

Answer:

If pollination does not occur then fertilization cannot take place because male gametes will not be available. For fertilization both male and female gametes must be present.