Question

Arrange the following stages of development of a dicot embryo in the order of their occurrence: (i) Formation of heart shaped embryo
(ii) Formation of typical dicot embryo
(iii) Formation of zygote
(iv) Formation of globular embryo

• A. (i), (ii), (iii), (iv)
• B. (iii), (iv), (i), (ii)
• C. (iii), (i), (ii), (iv)
• D. (iv), (i), (ii), (iii)

Hint:

Embryo development is irreversible and strictly sequential; skipping stages is biologically impossible.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Embryogenesis in dicots follows a programmed sequence of cell divisions starting from the fertilized egg (zygote) through several morphologically distinct stages to form a mature embryo.
Step 2: Detailed Explanation:
The developmental sequence occurs as follows:
1. Formation of zygote (iii): The fusion of male and female gametes marks the beginning.
2. Formation of globular embryo (iv): The proembryo undergoes divisions to form a spherical, globular structure.
3. Formation of heart shaped embryo (i): Further differentiation leads to the development of cotyledons, creating a heart-like shape.
4. Formation of typical dicot embryo (ii): The embryo matures with two cotyledons and the embryonic axis.

This progression ensures the necessary structural maturation for germination.
Step 3: Final Answer:
The correct chronological order is (iii), (iv), (i), (ii), which corresponds to option (B).