Which one is antagonist to GAs

Options

A. NAA
B. Zeatin
C. ABA
D. Ethylene

Answer

To determine which hormone acts as an antagonist to gibberellic acid (GA), we can analyze the options provided:

1. **Understanding Gibberellic Acid (GA)**:
- Gibberellic acid is a plant hormone that promotes growth in various parts of the plant. It is produced in the roots, young leaves, and embryos. Its primary function is to act as a plant growth regulator.

2. **Identifying the Antagonist**:
- An antagonist in this context is a substance that counteracts the effects of gibberellic acid. We need to find a hormone that inhibits growth or has opposite effects to GA.

3. **Analyzing the Options**:
- **NAA (Naphthalene Acetic Acid)**: This is a synthetic auxin that promotes growth, so it cannot be the antagonist.
- **ZRT (Cytokinin)**: Cytokinins promote cell division and growth, thus not acting as an antagonist to GA.
- **ABA (Abscisic Acid)**: This hormone is known to inhibit growth and promote senescence (aging) of leaves. It induces dormancy, which is opposite to the effects of GA that breaks dormancy.
- **Ethylene**: This hormone is involved in various growth processes but does not act as an antagonist to GA.

4. **Conclusion**:
- Based on the analysis, the hormone that acts as an antagonist to gibberellic acid is **Abscisic Acid (ABA)**.

### Final Answer:
The antagonist to gibberellic acid (GA) is **Abscisic Acid (ABA)**.