Respiratory climacteric is brought about by which of the following hormones ?

Options

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

Answer

To solve the question regarding which hormone is responsible for respiratory climacteric, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Respiratory Climacteric**:
- Respiratory climacteric refers to a significant increase in the rate of respiration that occurs in fruits during the ripening process. This is often associated with the production of ethylene.

2. **Identify the Hormones Listed in the Options**:
- The options provided are:
- Auxin
- Gibberellins
- Ethylene
- Cytokinin

3. **Analyze Each Hormone**:
- **Auxin**: Primarily involved in cell elongation and growth regulation but not directly linked to respiratory climacteric.
- **Gibberellins**: Involved in promoting growth and seed germination but not specifically related to respiration during ripening.
- **Cytokinin**: Primarily involved in cell division and growth, particularly in shoots, but does not play a significant role in respiratory climacteric.
- **Ethylene**: A gaseous plant hormone known to regulate fruit ripening and is directly associated with increased respiration rates during this process.

4. **Conclude the Correct Answer**:
- Based on the analysis, ethylene is the hormone responsible for the respiratory climacteric as it enhances respiration during the ripening of fruits.

### Final Answer:
The correct answer is **ethylene**.

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