How many of the following meristems are completely secondary in origin ?
A. Cork cambium of a dicot stem
B. Vascular cambium of a dicot stem
C. Cork cambium of a dicot root
D. Vascular cambium of a dicot root

Options

A. `4`
B. `3`
C. `2`
D. `1`

Answer

To determine how many of the given meristems are completely secondary in origin, we need to analyze each option provided:

1. **Cork cambium of a dicot stem**:
- The cork cambium is a secondary meristem. It arises from the outer layers of the stem and contributes to the formation of cork, which is part of the periderm. This is a secondary growth process, so it is completely secondary in origin.

2. **Vascular cambium of a dicot stem**:
- The vascular cambium is also a secondary meristem. It forms between the xylem and phloem and is responsible for the secondary growth of vascular tissues. Therefore, it is completely secondary in origin.

3. **Cork cambium of a dicot root**:
- Similar to the cork cambium in the stem, the cork cambium in the root is a secondary meristem. It develops from the pericycle and contributes to the formation of cork, making it also completely secondary in origin.

4. **Vascular cambium of a dicot root**:
- The vascular cambium in the root functions similarly to that in the stem, facilitating secondary growth by producing additional xylem and phloem. Thus, it is also completely secondary in origin.

Now, summarizing the analysis:
- All four options (A, B, C, and D) are completely secondary in origin.

**Final Answer**: All four meristems (A, B, C, and D) are completely secondary in origin.