A hormone delaying senescence is

Options

A. auxin
B. cytokinin
C. ethylene
D. gibberellin

Answer

To determine which hormone delays senescence in plants, we can analyze the functions of the hormones provided in the question: auxin, cytokinin, ethylene, and zyberlin.

### Step-by-Step Solution:

1. **Understanding Senescence**:
- Senescence is the process of aging in plants, which leads to the deterioration of cells and tissues. It is important to identify hormones that can delay this process.

2. **Analyzing Auxin**:
- Auxin is primarily involved in processes such as apical dominance and parthenocarpy (development of fruit without fertilization).
- It does not play a significant role in delaying senescence.

3. **Analyzing Cytokinin**:
- Cytokinin is known for promoting cell division and growth.
- One of its key functions is to delay leaf senescence by promoting nutrient mobilization and overcoming apical dominance.
- This makes cytokinin a strong candidate for delaying the aging process in plants.

4. **Analyzing Ethylene**:
- Ethylene is a hormone that primarily regulates fruit ripening and is associated with the aging process rather than delaying it.
- It accelerates senescence rather than delaying it.

5. **Analyzing Zyberlin**:
- Zyberlin is involved in increasing internodal length and plays a role in seed germination and bolting.
- It does not have a significant effect on delaying senescence.

6. **Conclusion**:
- Based on the analysis, the hormone that effectively delays senescence is **Cytokinin**.

### Final Answer:
The hormone delaying senescence is **Cytokinin**.

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