The vascular bundles of a dicot stem are

Options

A. closed, collateral and exarch
B. open, collateral and exarch
C. closed, collateral and endarch
D. open, collateral and endarch

Answer

### Step-by-Step Solution:

1. **Understanding Vascular Bundles**:
- Vascular bundles are groups of xylem and phloem tissues that transport water, nutrients, and food throughout the plant.

2. **Identifying the Type of Plant**:
- The question specifies "dicot stem." Dicotyledons (dicots) are a group of flowering plants that typically have two seed leaves.

3. **Recognizing Secondary Growth**:
- In dicot stems, secondary growth occurs, which is characterized by the presence of vascular cambium. This cambium allows for the formation of new xylem and phloem, indicating that the vascular bundles are "open."

4. **Determining the Arrangement of Xylem and Phloem**:
- In dicot stems, the xylem is located towards the center (inner side) and the phloem is located towards the outside (outer side). This arrangement is referred to as "collateral."

5. **Understanding the Terms Endarch and Exarch**:
- In vascular bundles, "endarch" means that the protoxylem (the first-formed xylem) is located towards the center (pith), while "exarch" means that the protoxylem is located towards the outside. In dicot stems, the protoxylem is towards the pith, making it "endarch."

6. **Evaluating the Options**:
- Now, we can evaluate the provided options:
- **Option 1**: Closed collateral exarch - Incorrect (they are open and endarch).
- **Option 2**: Open collateral exarch - Incorrect (they are open but endarch).
- **Option 3**: Closed collateral endarch - Incorrect (they are open).
- **Option 4**: Open collateral endarch - Correct (they are open, collateral, and endarch).

7. **Conclusion**:
- The correct answer is **Option 4: Open collateral endarch**.