Which of the following phytohormone is a derivative of carotenoids?

Options

A. Auxin
B. ABA
C. Ethylene
D. Cytokinin

Answer

To determine which phytohormone is a derivative of carotenoids, we can analyze the options provided:

1. **Auxin**: Auxin is primarily derived from the amino acid tryptophan. It plays a key role in plant growth, particularly in apical dominance and cell elongation. Therefore, auxin is not derived from carotenoids.

2. **Abscisic Acid (ABA)**: Abscisic acid is indeed a derivative of carotenoids. It is often referred to as the stress hormone because it helps plants respond to stress conditions, such as drought. This makes ABA the correct answer to the question.

3. **Ethylene**: Ethylene is a gaseous hormone involved in various plant processes, including fruit ripening and leaf abscission. It is not derived from carotenoids.

4. **Cytokinin**: Cytokinins are a class of plant hormones that promote cell division and growth. They are derived from purines, specifically adenine, and are not related to carotenoids.

After analyzing each option, we conclude that the phytohormone that is a derivative of carotenoids is **Abscisic Acid (ABA)**.

### Final Answer:
The phytohormone that is a derivative of carotenoids is **Abscisic Acid (ABA)**.