Which one of the plant growth regulators would you use if you are asked to
delay leaf senescence.

Answer

To answer the question about which plant growth regulator can be used to delay leaf senescence, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Leaf Senescence**:
- Leaf senescence refers to the aging process of leaves, which leads to their eventual death. It is a natural process influenced by various factors, including environmental conditions and hormonal balance.

2. **Identify Plant Growth Regulators**:
- Plant growth regulators (PGRs) are chemicals that influence plant growth and development. Some common types include auxins, gibberellins, cytokinins, abscisic acid, and ethylene.

3. **Focus on the Role of Cytokinins**:
- Cytokinins are a class of PGRs known for their role in promoting cell division and growth. They are particularly effective in delaying senescence in leaves.

4. **Conclude that Cytokinins Delay Leaf Senescence**:
- Among the various plant growth regulators, cytokinins are specifically known to inhibit the aging process in leaves, thereby delaying senescence.

5. **Final Answer**:
- The plant growth regulator that would be used to delay leaf senescence is **Cytokinins**.