Question

Describe the events that take place during fertilization in an angiosperm.

Answer 1

1. The pollen tube grows from the pollen grain deposited on the stigma, passes through the style, and reaches the ovary toward the ovule.
2. The pollen tube then enters the ovule through the micropyle, a process known as porogamy.
3. The pollen tube penetrates the embryo sac at the micropylar end.
4. The tip of the pollen tube bursts, releasing the two male gametes into the embryo sac.
5. One male gamete fuses with the egg cell, forming a diploid zygote (2n). This process is called syngamy.
6. The other male gamete fuses with the two polar nuclei in the central cell to form a triploid primary endosperm nucleus (3n). This is known as triple fusion.
7. The combined process of syngamy and triple fusion is termed double fertilization, which is a unique feature of angiosperms.
8. The diploid zygote develops into an embryo.
9. The primary endosperm nucleus divides repeatedly to form the endosperm, which nourishes the developing embryo.
10. After fertilization, the ovule matures into a seed, and the ovary develops into a fruit.