In Polygonum ,

Options

A. ovule is orthotropic with an endosporic embryo sac derived from a single chalazal megaspore
B. ovule is orthotropic with an endosporic embryo sac derived from a single micropylar megaspore
C. ovule is anatropous with an endosporic embryo sac derived from a single chalazal megaspore
D. ovule is anatropous with an endosporic embryo sac derived from a single micropylar megaspore

Answer

To solve the question regarding Polygonum, we need to analyze the statements provided and determine which one is correct based on the characteristics of the embryo sac in Polygonum.

### Step-by-Step Solution:

1. **Understanding the Embryo Sac in Polygonum**:
- Polygonum has a **monosporic embryo sac**. This means that the embryo sac develops from one functional megaspore.
- The functional megaspore is located at the **chalazal end** of the ovule.

2. **Formation of Megaspores**:
- The megaspore mother cell (MMC) undergoes meiosis to produce **four megaspores**.
- Out of these four megaspores, only **one megaspore remains functional**, while the other three degenerate.

3. **Development of the Embryo Sac**:
- The functional haploid megaspore enlarges and develops into an **8-nucleate embryo sac**.
- The type of embryo sac in Polygonum is described as **orthotropic**.

4. **Characteristics of Orthotropic Embryo Sac**:
- In an orthotropic embryo sac, the ovule is **erect** and does not exhibit curvature.
- The hilum, chalaza, and micropyle are aligned along the **same vertical axis**.

5. **Evaluating the Statements**:
- **Statement A**: "Ovule is orthotropic with an endosporic embryo sac derived from a single chalazal megaspore."
- This statement is **correct**.
- **Statement B**: "Ovule is orthotropic with an endosporic embryo sac which is derived from a single micropilar megaspore."
- This statement is **incorrect** because the megaspore is chalazal, not micropilar.
- **Statement C**: "Ovule is anatropous with an endosporic embryo sac derived from a single chalazal megaspore."
- This statement is **incorrect** because the ovule is orthotropic, not anatropous.
- **Statement D**: "Ovule is anatropous with an endosporic embryo sac derived from a single micropilar megaspore."
- This statement is also **incorrect** for the same reasons as C.

6. **Conclusion**:
- The only correct statement is **Statement A**. Therefore, the answer to the question is **A**.