What happens to primary phloem in stem after secondary growth?
(a) Compresses outside and degenerates
(b) Compresses inside and degenerates
(c) Becomes part of secondary phloem
(d) Modifies in sclerenchyma

Options

A. Compresses outside and degenerates
B. Compresses inside and degenerates
C. Becomes part of sec phloem
D. Modifies in sclerenchyma

Answer

To answer the question "What happens to primary phloem in stem after secondary growth?", we can analyze the options step by step.

### Step-by-Step Solution:

1. **Understanding Secondary Growth**:
- Secondary growth in plants is primarily facilitated by the vascular cambium, which produces secondary tissues.
- The vascular cambium is responsible for the production of secondary phloem and secondary xylem.

2. **Production of Secondary Phloem**:
- The secondary phloem is produced centrifugally, meaning it is formed away from the center of the stem.
- As new secondary phloem cells are produced, they push the existing primary phloem outward.

3. **Effect on Primary Phloem**:
- The primary phloem, which was present before secondary growth, gets compressed due to the formation of new secondary phloem.
- Additionally, the newly formed secondary xylem (which is produced centripetally, towards the center) also exerts pressure on the primary phloem.

4. **Degeneration of Primary Phloem**:
- As a result of being pushed outward and compressed by the secondary phloem and secondary xylem, the primary phloem becomes functionless.
- Eventually, the primary phloem degenerates due to this compression and lack of function.

5. **Conclusion**:
- The primary phloem is compressed outward and degenerates as a result of secondary growth.
- Therefore, the correct answer to the question is **(a) Compresses outside and degenerates**.