Embryo sac of flowering plants develops from

Options

A. Zygote
B. Megaspore
C. Nucellus
D. Embryo.

Answer

To answer the question "Embryo sac of flowering plants develops from," we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Origin of the Embryo Sac**:
- The embryo sac is a crucial structure in flowering plants (angiosperms) that plays a significant role in reproduction.

2. **Understand the Role of the Megaspore Mother Cell**:
- Inside the ovule, there is a structure called the nucellus, which contains the megaspore mother cell (also known as the megasporangium).

3. **Meiotic Division**:
- The megaspore mother cell undergoes meiotic division, which is a type of cell division that reduces the chromosome number by half. This process produces four haploid megaspores.

4. **Degeneration of Megaspores**:
- Out of the four megaspores formed, three typically degenerate, leaving only one functional megaspore.

5. **Mitosis of the Functional Megaspore**:
- The remaining functional megaspore undergoes mitotic divisions. Specifically, it undergoes three rounds of mitosis without any cytoplasmic division, leading to the formation of eight nuclei.

6. **Formation of the Embryo Sac**:
- These eight nuclei are then organized into a structure known as the embryo sac. This structure consists of seven cells: one egg cell, two synergids, one central cell (which contains two polar nuclei), and three antipodal cells.

7. **Conclusion**:
- Therefore, the embryo sac of flowering plants develops specifically from the megaspore.

### Final Answer:
The embryo sac of flowering plants develops from **megaspore** (Option B).

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