Which one prevents photo-oxidation and pigment destruction? 

Options

A. Phytochrome
B. Phytohormone
C. Phycocyanin
D. Phyco-erythrin.

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks which component prevents photo-oxidation and pigment destruction in plants.

2. **Identifying the Options**: The options provided are:
- a) Phytochrome
- b) Phytohormone
- c) Phycocyanin
- d) Phycoerythrin

3. **Analyzing Phytochrome**:
- Phytochromes are pigments found in plants that play a crucial role in photoperiodism, which is the response of plants to the relative lengths of light and dark periods.
- They help in preventing photo-oxidation, which is the damage caused by light-induced reactions that generate free radicals.
- Phytochromes also protect chlorophyll and other pigments from destruction.

4. **Analyzing Phytohormone**:
- Phytohormones are plant hormones that regulate growth and development but do not directly prevent photo-oxidation or pigment destruction.
- Therefore, this option is incorrect.

5. **Analyzing Phycocyanin**:
- Phycocyanin is an accessory pigment found in cyanobacteria and some algae, but it does not play a significant role in preventing photo-oxidation in plants.
- Hence, this option is also incorrect.

6. **Analyzing Phycoerythrin**:
- Phycoerythrin is a red pigment found in certain algae and cyanobacteria, and like phycocyanin, it does not prevent photo-oxidation in plants.
- Thus, this option is incorrect as well.

7. **Conclusion**: After analyzing all the options, the correct answer is **Phytochrome** as it prevents photo-oxidation and pigment destruction.

### Final Answer:
The component that prevents photo-oxidation and pigment destruction is **Phytochrome**.

---