The hormone which can replace the long days and low temperature requirement for flowering in some plants is
(a) Gibberellin
(b) Cytokinin
(c) Vernalin
(d) Ethylene

Options

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

Answer

To solve the question regarding which hormone can replace the long days and low temperature requirement for flowering in some plants, we can follow these steps:

### Step 1: Understand the Question
The question asks for a specific hormone that can substitute the requirements of long days and low temperatures for flowering in certain plants. This indicates that we are looking for a hormone involved in the flowering process.

### Step 2: Analyze the Options
We have four options to consider:
- (a) Gibberellin
- (b) Cytokinin
- (c) Vernalin
- (d) Ethylene

### Step 3: Recall the Functions of Each Hormone
- **Gibberellin**: Known for promoting growth and flowering, especially in long-day plants. It can also substitute for the low temperature requirement in biennials, a process known as vernalization.
- **Cytokinin**: Primarily involved in cell division and growth, but not specifically in flowering.
- **Vernalin**: This is not a commonly recognized hormone in plant physiology; it seems to be a misnomer for vernalization, which is a process rather than a hormone.
- **Ethylene**: Involved in fruit ripening and other processes, but not specifically in replacing long day or low temperature requirements for flowering.

### Step 4: Identify the Correct Answer
From the analysis, gibberellin is the hormone that can replace the long day and low temperature requirement for flowering, particularly in biennial plants. Therefore, the correct answer is:
**(a) Gibberellin**

### Step 5: Confirm the Answer
Gibberellins are indeed used in agriculture to induce flowering and can act as a substitute for cold temperatures in the vernalization process. This confirms that our choice is correct.

### Final Answer
The hormone which can replace the long days and low temperature requirement for flowering in some plants is:
**(a) Gibberellin**

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