The hormone responsible for nutrient mobilization which helps in the delay of leaf senescence is

Options

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

Answer

To solve the question regarding the hormone responsible for nutrient mobilization which helps in the delay of leaf senescence, we can follow these steps:

### Step 1: Understand the Key Terms
- **Nutrient Mobilization**: This refers to the process by which nutrients are moved from storage tissues to growing tissues in plants.
- **Leaf Senescence**: This is the process of aging in leaves, which often leads to their eventual death.

### Step 2: Analyze the Hormones
1. **Auxin**: Primarily involved in apical dominance and cell elongation. It does not play a significant role in nutrient mobilization or delaying senescence.
2. **Zebulin**: This hormone is less commonly mentioned in plant physiology and is not primarily known for nutrient mobilization or delaying senescence.
3. **Cytokinin**: This hormone promotes cell division and is known to help in nutrient mobilization. Importantly, it also delays leaf senescence by promoting the retention of chlorophyll and preventing the aging process in leaves.
4. **Ethylene**: This hormone is primarily associated with fruit ripening and does not delay senescence; rather, it can promote it in some cases.

### Step 3: Identify the Correct Answer
Based on the analysis, the hormone that is responsible for nutrient mobilization and helps in delaying leaf senescence is **Cytokinin**.

### Final Answer
The correct answer is **Cytokinin**.

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