Question

Following are the diagrams of entry of pollen tube into ovule. Identify the type A and B.

Hint:

Double fertilization is a hallmark of angiosperms, ensuring the efficient use of resources and proper seed development.

Answer 1

Step 1: Understanding the diagrams.
The diagrams represent the process of pollen tube entry into the ovule, which is an essential part of fertilization in flowering plants.
- Diagram A: This represents the Monosporic type of embryo sac where the pollen tube enters the ovule through the micropyle and directly reaches the embryo sac for fertilization.
- Diagram B: This represents the Bisporic type of embryo sac where the pollen tube enters through the micropyle and interacts with the two synergid cells before reaching the egg cell for fertilization.
Step 2: Conclusion.
- A represents the monosporic embryo sac. - B represents the bisporic embryo sac.
ii. Give any four points of significance of double fertilization.
Solution:
Step 1: Understanding Double Fertilization.
Double fertilization is a unique process in angiosperms where two fertilization events occur within the ovule. The two sperm cells from the pollen tube fuse with different cells in the embryo sac.
Step 2: Significance of Double Fertilization.
1. Formation of Zygote and Endosperm: One sperm cell fertilizes the egg cell to form the zygote, while the other sperm cell fuses with the central cell to form the endosperm, which nourishes the developing embryo.
2. Efficient Use of Resources: Double fertilization ensures that the endosperm is only formed when fertilization occurs, saving energy and resources.
3. Prevention of Unnecessary Development: It prevents the unnecessary development of endosperm in the absence of fertilization, ensuring better resource allocation.
4. Formation of Seeds: Double fertilization leads to the formation of seeds that are capable of germination, ensuring plant propagation.
Step 3: Conclusion.
Double fertilization is crucial for the development of seeds, ensuring both the formation of the embryo and the nourishing endosperm.