During the process of fertilisation which among the following is the most commom way of pollen tube entry into the embryo sac ?

Porogamy

The correct answer is Option (2) →Porogamy

The pollen grain germinates on the stigma to produce a pollen tube through one of the germ pores. The contents of the pollen grain move into the pollen tube. Pollen tube grows through the tissues of the stigma and style and reaches the ovary Pollen tube, after reaching the ovary, enters the ovule through the micropyle and then enters one of the synergids through the filiform apparatus.The pollen tube follows the three routes to reach the ovule for the purpose of fertilization. These three points are porogamy, mesogamy and chalazogamy.

(1) Porogamy: After reaching the ovary, the pollen tube enters the ovule, through micropylar end, e.g., Lily.

(2) Mesogamy:  After reaching the ovary, the pollen tube enters the ovule, through laterally end, e.g., Cucurbita.

(3) Chalazogamy: After reaching the ovary, the pollen tube enters the ovule, through chalazal end, e.g., Casuarina

Porogamy is most common ,chalazogamy is less common and mesogamy is rare. In porogamy the tip of pollen tube enters the micropyle ,pushes through the nucellar tissue and finally pierces the egg-apparatus end of the embryo sac.