Which one includes growth promoters?

Options

A. Auxin, Cytokinin, ABA
B. GA, Cytokinin, `C_2 H_4`
C. `C_2 H_4 , ABA`
D. Auxin, Cytokinin, GA

Answer

To determine which option includes growth promoters, we need to analyze the provided options based on our understanding of plant growth regulators (PGRs).

### Step-by-Step Solution:

1. **Understanding Plant Growth Regulators (PGRs)**:
- PGRs are substances that influence plant growth and development. They can be classified into two categories: growth promoters and growth inhibitors.

2. **Identifying Growth Promoters**:
- Growth promoters are substances that enhance plant growth processes such as cell division, cell enlargement, flowering, and fruiting. Common examples include:
- Auxins
- Gibberellic acid
- Cytokinins

3. **Identifying Growth Inhibitors**:
- Growth inhibitors, on the other hand, hinder plant growth and can induce dormancy or abscission. Examples include:
- Abscisic acid (ABA)
- Ethylene (C2H4) - while it can promote certain processes, it is primarily categorized as an inhibitor.

4. **Analyzing the Options**:
- **Option 1**: Auxin, Cytokinin, and ABA
- **Analysis**: ABA is a growth inhibitor. Therefore, this option does not contain only growth promoters.
- **Option 2**: Gibberellic acid, Cytokinin, and Ethylene (C2H4)
- **Analysis**: Ethylene is primarily an inhibitor. Thus, this option does not contain only growth promoters.
- **Option 3**: Ethylene (C2H4) and Abscisic acid
- **Analysis**: Both are growth inhibitors. This option does not contain any growth promoters.
- **Option 4**: Auxin, Cytokinin, and Gibberellic acid
- **Analysis**: All three are recognized growth promoters. This option contains only growth promoters.

5. **Conclusion**:
- The correct answer is **Option 4: Auxin, Cytokinin, and Gibberellic acid**, as it includes only growth promoters.