What is the position of protoxylem in secondary xylem ?

Options

A. Exarch
B. Endarch
C. Mesarch
D. None of the above

Answer

To answer the question regarding the position of protoxylem in secondary xylem, we can break down the explanation into clear steps:

### Step-by-Step Solution:

1. **Understanding Xylem Types**:
- Xylem is composed of two main types: primary xylem and secondary xylem.
- Primary xylem is formed during the initial stages of plant growth, while secondary xylem is produced later by the activity of the vascular cambium.

2. **Role of Cambium**:
- The vascular cambium is a layer of meristematic tissue that is responsible for the production of secondary xylem and secondary phloem.
- When the cambium becomes active, it divides and produces new cells both inward (towards the center of the stem) and outward (towards the outside).

3. **Crushing of Primary Xylem**:
- As the cambium produces new cells, the existing primary xylem and primary phloem can become crushed due to the pressure from the newly formed secondary xylem and phloem.
- In many cases, the primary xylem is completely crushed, while some primary phloem may remain intact.

4. **Position of Protoxylem**:
- Protoxylem is the first-formed xylem and is part of the primary xylem.
- In the context of secondary xylem, the protoxylem does not have a distinct position because it gets crushed during the formation of secondary xylem.
- Therefore, in secondary xylem, there is no clear differentiation or division of protoxylem and metaxylem as seen in primary xylem.

5. **Conclusion**:
- The position of protoxylem in secondary xylem is essentially non-existent as it gets crushed and is not distinguishable in the secondary xylem structure.

### Final Answer:
The position of protoxylem in secondary xylem is that it is crushed and not distinguishable; hence, it is effectively absent in the structure of secondary xylem.

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