In old sieve tubes at the end of growing season, which of the following gets deposited over sieve plate to regulate sugar transport :

Options

A. P-protein
B. Callose
C. Lignin
D. ABA

Answer

To solve the question regarding what gets deposited over the sieve plate in old sieve tubes at the end of the growing season to regulate sugar transport, follow these steps:

### Step-by-Step Solution:

1. **Understand the Context**: Recognize that the question pertains to the functioning of sieve tubes in plants, particularly at the end of the growing season when sugar transport is crucial.

2. **Identify the Options**: The options provided are:
- P-protein
- Callose
- Lignin
- ABA (Abscisic Acid)

3. **Analyze Each Option**:
- **P-protein**: This is a type of protein found in the phloem sap but does not specifically regulate sugar transport over the sieve plate.
- **Callose**: This is a carbohydrate that forms a plug at the sieve plates, particularly during times when the plant needs to regulate or stop the flow of nutrients, such as at the end of the growing season.
- **Lignin**: This is a structural component that provides rigidity to cell walls but is not involved in regulating sugar transport in sieve tubes.
- **ABA (Abscisic Acid)**: This hormone is involved in processes like seed dormancy and does not play a direct role in sugar transport through sieve tubes.

4. **Determine the Correct Answer**: Given the analysis, callose is specifically known to be deposited over the sieve plates to regulate sugar transport, especially at the end of the growing season when the plant may need to manage its resources.

5. **Conclude**: Therefore, the correct answer to the question is **Callose**.

### Final Answer:
**Callose** (Option B) is deposited over the sieve plate in old sieve tubes to regulate sugar transport at the end of the growing season.

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