Question

mention the changes in flower undergoes after fertilisation

Answer 1

After fertilization the petals, in stanon and Carole fall off and only sepal, ovary and ovuel remain . This is because after fertilization the ovary develop into fruit and protect the seed , these seeds are actually fertilized ovuel. But , carpel and petals do not have any role after fertilization so they fall off .

Answer 2

After fertilization, the following changes are observed in a flower:

There is formation of a diploid zygote and it develops into an embryo, which forms the future plant.  

The endosperm cells serve as a source of nutrition for the developing embryo.

The ovule becomes the seed.

The ovary becomes the fruit.

In most of the plants the antipodals and synnergids disintegrate before, during or immediately after fertilization.

The outer and inner integuments of the ovule become the testa or the seed coat of the seed.  

Petals and sepals fall off.