The hormone capable of replacing the requirement of long photoperiod for flowering is:

Options

A. Ethylene
B. Auxin
C. Gibberellin
D. Cytokinin

Answer

To solve the question regarding which hormone can replace the requirement of long photoperiod for flowering, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Context**:
- Long photoperiod is essential for certain plants known as long-day plants. These plants require more light than a critical limit to initiate flowering.

2. **Evaluate the Options**:
- **Option A: Ethylene**
- Ethylene is primarily involved in fruit ripening and does not play a significant role in promoting flowering in long-day plants.
- **Option B: Auxin**
- Auxin is a plant hormone that promotes root and shoot development but is not directly responsible for flowering.
- **Option C: Gibberellin**
- Gibberellin is a plant hormone that promotes growth and flowering. It can substitute for the long photoperiod requirement in flowering plants.
- **Option D: Cytokinin**
- Cytokinin is involved in cell division and growth but does not specifically replace the need for long photoperiod for flowering.

3. **Identify the Correct Answer**:
- Among the options evaluated, Gibberellin (Option C) is the hormone that can replace the requirement of long photoperiod for flowering in long-day plants.

### Final Answer:
The hormone capable of replacing the requirement of long photoperiod for flowering is **Gibberellin** (Option C).

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