Which among the following is not a post-fertilisation events ?

(A) Endosperm  development.

(B) Maturation of ovule(s) into seed(s) .

(C) Maturation of  ovary into fruit.

(D) Embryo development .

(E) Pollen grains development .

Choose the correct answer from the given options .

Only E 

The correct answer is Option (4): Only E
Following double fertilisation, events of endosperm and embryo development, maturation of ovule(s) into seed(s) and ovary into fruit, are collectively termed post-fertilisation events.

Pollen grains development is a pre -fertilization event. Pollen grain development occurs prior to fertilization. Pollen grains are produced in the anthers of the flower through the process of microsporogenesis. They contain the male gametes (sperm cells) necessary for fertilization.

The other options listed are all post-fertilization events:

(A) Endosperm development:  After fertilization, the endosperm develops from the fusion of the male gamete with the polar nuclei in the central cell. It provides nourishment to the developing embryo.

(B) Maturation of ovule(s) into seed(s):  Following fertilization, the ovules within the ovary develop into seeds. This involves the transformation of the ovule structures, such as the integuments, into the protective seed coat, and the development of the embryo within the seed.

(C) Maturation of ovary into fruit:  After fertilization, the ovary undergoes changes and develops into a fruit. The walls of the ovary thicken and form the pericarp, which surrounds and protects the developing seeds.

(D) Embryo development:  Following fertilization, the zygote develops into an embryo within the seed. Embryo development includes the differentiation and growth of various embryonic structures, such as the root, shoot, and cotyledons.

Therefore, among the given options, (E) Pollen grains development is not a post-fertilization event but rather a pre-fertilization process necessary for successful pollination and subsequent fertilization to occur.