Question

Double fertilization involves
A. Fusion of secondary nucleus with both male gametes
B. Fusion of secondary nucleus with one male gamete
C. Fusion of one nucleus with one male gamete
D. All of the above

Answer 1

Double fertilization is a phenomenon occurring in plants. It occurs in angiosperms. Syngamy and triple fusion both happen in double fertilization.

Complete answer:
The embryo sac is the female uterus in case of plants. The embryo sac has an egg apparatus. The egg apparatus has three antipodal cells. Below this lies one big central cell which has two polar nuclei. Below this is the lower region where the two synergids and the one egg lie. The synergids have a filiform apparatus. It directs the pollen tube into the egg cell.

- The pollen tube contains male gamete which fuses with the egg cell and forms zygote and endosperm.
- The male gamete first fuses with synergids and then with the central cell.
- So the double fertilization involves the fusion of secondary nuclei with one male gamete.
- Two polar nuclei when fused together makes a secondary nucleus. It is also known as primary endosperm nucleus (PEM). primary endosperm nucleus cells are filled with reserve food materials and hence it provides nourishment to the developing embryo.

Therefore the correct answer is option ‘A’.

Note: Microspore divides mitotically to form a vegetative cell and a generative cell. The vegetative cell extends the pollen tube to transport pollen. Vegetative cells are non-motile.