Which of the following is not a part of a typical embryo sac formation in angiosperms ?

Options

A. The MMC undergoes meiotic division to form 4 megaspores.
B. Three mitotic divisions occur in a megaspore to form an eight nucleate stage.
C. The cell walls are formed with 3 cells grouped together at chalazal end, together called the egg apparatus.
D. The egg apparatus contains two synergids and one egg cell .

Answer

To determine which of the following is not a part of a typical embryo sac formation in angiosperms, we need to understand the structure and formation of the embryo sac.

### Step-by-Step Solution:

1. **Understanding Embryo Sac**: The embryo sac is the female gametophyte in angiosperms and is crucial for sexual reproduction. It is formed within the ovule, which is located in the ovary of the carpel.

2. **Formation Process**: The embryo sac formation begins with a diploid cell known as the megaspore mother cell (MMC). This cell undergoes meiosis to produce four haploid megaspores. Typically, three of these megaspores degenerate, leaving one functional megaspore.

3. **Mitotic Divisions**: The surviving megaspore undergoes three rounds of mitotic divisions. This results in the formation of an 8-nucleate structure, which eventually organizes into a 7-celled embryo sac.

4. **Cell Types in the Embryo Sac**:
- At the micropylar end, there are three cells known as the egg apparatus, which consists of two synergids and one egg cell.
- At the chalazal end, there are three antipodal cells.
- The central cell contains two polar nuclei.

5. **Identifying the Incorrect Option**:
- The options provided in the question likely include statements about the structure and formation of the embryo sac.
- We need to identify which statement does not accurately describe the typical formation or structure of the embryo sac.

6. **Analyzing the Options**:
- If an option states that the egg apparatus is located at the chalazal end, this would be incorrect, as the egg apparatus is located at the micropylar end.

7. **Conclusion**: Based on the analysis, the option that incorrectly describes the embryo sac formation is the one that states the egg apparatus is at the chalazal end.

### Final Answer:
The option that is not a part of a typical embryo sac formation in angiosperms is the one stating that the egg apparatus is located at the chalazal end.

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