Growth regulator ethylene is used for

Options

A. Retarding ripening of tomatoes
B. Speeding up ripening of fruits
C. Slowing down ripening of apples
D. Both B and C.

Answer

### Step-by-Step Solution:

1. **Understanding Ethylene**: Ethylene is a plant growth regulator known primarily for its role in the ripening of fruits. It is often referred to as the "ripening hormone."

2. **Function of Ethylene**: The primary function of ethylene is to speed up the ripening process of fruits. This means that when ethylene is present, it accelerates the transformation of fruits from an immature state to a ripe state.

3. **Effects of Ethylene on Ripening**: The ripening process induced by ethylene is accompanied by an increased rate of respiration in the fruit. This heightened respiration leads to the breakdown of complex carbohydrates into simple sugars, which contributes to the sweetness of the fruit.

4. **Physical Changes During Ripening**: As ripening progresses, the cell walls of the fruit soften due to the action of ethylene. This softening is a key characteristic of ripe fruits, making them more palatable.

5. **Analyzing the Options**:
- **Option A**: Retarding ripening of tomatoes – This is incorrect because ethylene does not retard ripening; it accelerates it.
- **Option B**: Speeding up ripening of fruits – This is correct as it aligns with the known function of ethylene.
- **Option C**: Slowing down ripening of apples – This is also incorrect for the same reason as option A.
- **Option D**: Both B and C – Since option C is incorrect, this option is also incorrect.

6. **Conclusion**: The correct answer is **Option B**: Speeding up ripening of fruits.