Question

Double fertilization is an exclusive feature found in flowering plants. Based on the course of the growth of pollen tube and entry into the ovule which one of the following is known as mesogamy?
a. Entry of pollen tube through the micropyle into the ovule
b. Entry of pollen tube through the placenta and the funiculus
c. Entry of pollen tube through the integuments
d. Entry of pollen tube through the funiculus and chalaza into the embryo sac from the egg apparatus end

Answer 1

Hint: Double fertilization is a technique of fertilization characterized by the fusion of a woman gametophyte with male gametes. In this mechanism, one sperm cell fuses with the egg-producing zygote, and the other fuses with the two polar nuclei to make the endosperm. All angiosperm flora go through a double fertilization procedure.

Complete answer:
- There are numerous methods via which the pollen tube can attain embryo sac for pollination.
- One of them is Porogamy, it is the condition in which the pollen tube enters the ovule from the micropylar end.
- Second is a term known as Chalazogamy, it is the situation where anthers or the pollen grain come into the pollen tube from chalaza.
- Chalaza is a tissue situated on the ovule near the polar end, when the pollen tube enters through the chalaza it destroys the embryo sac and other cells in the ovule except for the egg cell.
- Mesogamy is the mechanism in which pollen tube enters via the integuments, not from the micropyle or chalaza.
- Integuments are of two types, outer integuments present outside the ovule as a covering and inner integuments present inside the outer integuments layer.
- It enters through the antipodal cells.

Hence, the correct answer is option (C).

Note: Fusion of male and female gametes refers to fertilization or fusion of gametes. Fertilization can be defined as the fusion of the male gametes (pollen) with the female gametes (ovum) to form a diploid zygote. It is a physicochemical procedure which takes place after the pollination of the carpel. The entire series of this system takes area within the zygote to develop into a seed.