Question

Mesogamy is
A. Fusion of similar male and female gametes.
B.Fusion of morphologically different but physiologically similar gametes.
C.Entry of pollen tubes through the integument.
D.None of the above.

Answer 1

Hint:Pollen grains are present in the pollen tubes that enter the ovule through different ways. Then nucleus from the pollen grains fuses with the nucleus of the egg cell that is present in the ovule. Mesogamy is observed in the plants which includes pumpkin, gourds, etc.

Complete answer:
Fertilisation is the process of fusion of female and male gametes. In mesogamy, pollen tubes enter the ovule through the mid part of the ovule or through the integument of the ovule. Pollen tubes are the hollow tubes that arise from pollen grain when the pollen is aggregated on the stigma of the flower.
Pollen tubes deliver the male gametes inside the ovule. Because of this pollen tubes behave as a passenger that deliver sperm cells of the pollen grains. In mesogamy, integuments in the middle are pierced by the pollen tubes.

Additional information: There are many types by which the pollen tubes can reach in embryo sac for pollination. When the pollen tube enters into the ovule form the micropylar pore and this is known as porogamy. When the pollen tube enters into the ovule from the chalaza and this is known as chalazogamy.

Thus, the correct answer is option C. i.e., entry of pollen tubes through the integument.

Note:Mesogamy is the entry of pollen tubes through the integuments. There are three modes by which pollen tubes can enter i.e., mesogamy, porogamy and chalazogamy. The entry of pollen tubes is very much important because of the triple fusion to take place.