Which of the following is a modified from of adenine?

Options

A. Zeatin
B. NAA
C. Kinetin
D. Ethephon

Answer

To determine which of the given options is a modified form of adenine, we can analyze the options provided.

### Step-by-Step Solution:

1. **Understanding Adenine**: Adenine is a purine base that is one of the building blocks of DNA and RNA. It is also a component of various important biomolecules, including ATP (adenosine triphosphate) and certain plant hormones.

2. **Identifying the Options**: The question presents several options, and we need to evaluate each one to see if it is a modified form of adenine. The options mentioned are:
- ZRT (Zeatin)
- NAA (Naphthalene acetic acid)
- Cytokinin (a general term for a class of plant hormones)
- Atifone (which is likely a misspelling or misinterpretation of "Adenine" or "Adenosine")

3. **Analyzing Each Option**:
- **ZRT (Zeatin)**: This is a natural cytokinin that is derived from adenine. It is known to promote cell division and is indeed a modified form of adenine.
- **NAA (Naphthalene acetic acid)**: This is a synthetic auxin, not derived from adenine. It is used to promote root formation and growth but does not qualify as a modified form of adenine.
- **Cytokinin**: This is a class of plant hormones that includes zeatin. While zeatin is a cytokinin, the term itself does not refer to a specific modified form of adenine.
- **Atifone**: This term does not correspond to a recognized plant hormone or modified adenine derivative.

4. **Conclusion**: The only option that is a modified form of adenine is **ZRT (Zeatin)**.

### Final Answer:
The modified form of adenine is **ZRT (Zeatin)**.