Which of the following growth regulator helps to prevent fruit and leaf drop at early stage but promote the abscission of older mature leaves and fruits ?

Options

A. Auxin
B. GA
C. ABA
D. Ethylene

Answer

To solve the question regarding which growth regulator helps to prevent fruit and leaf drop at an early stage but promotes the abscission of older mature leaves and fruits, we can follow these steps:

### Step 1: Understand the Question
The question asks for a growth regulator that has two specific effects:
1. It prevents the drop of young fruits and leaves.
2. It promotes the shedding (abscission) of older leaves and fruits.

### Step 2: Identify the Options
The options provided are:
- Auxin
- Gibberellic Acid (GA)
- Abscisic Acid (ABA)
- Ethylene

### Step 3: Analyze Each Option
- **Auxin**: This growth regulator is known to delay the abscission of young leaves and fruits. It works by preventing the formation of the abscission zone, which is responsible for detaching parts of the plant. However, it can promote the abscission of older leaves and fruits.

- **Gibberellic Acid (GA)**: This hormone is primarily involved in promoting shoot elongation and does not play a significant role in preventing fruit and leaf drop.

- **Abscisic Acid (ABA)**: This hormone is associated with plant responses to stress, particularly in reducing water availability. It does not prevent the drop of young leaves and fruits.

- **Ethylene**: This hormone is known for its role in fruit ripening and can promote the abscission of fruits and leaves but does not prevent the drop of young ones.

### Step 4: Conclusion
Based on the analysis, **Auxin** is the correct answer as it prevents the drop of young leaves and fruits while promoting the abscission of older ones.

### Final Answer
The growth regulator that helps to prevent fruit and leaf drop at an early stage but promotes the abscission of older mature leaves and fruits is **Auxin**.

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