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 answer 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, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Sieve Tubes**: Sieve tubes are part of the phloem in plants and are responsible for the transport of sugars and other organic nutrients. They are composed of sieve elements that are aligned end to end.

2. **Structure of Sieve Plates**: At the ends of these sieve tubes, there are structures called sieve plates. These plates have numerous perforations that allow for the flow of sap (which contains sugars) between adjacent sieve elements.

3. **Function of Sieve Plates**: The sieve plates facilitate the movement of nutrients by connecting sieve tube elements. The perforations in the sieve plates are crucial for this transport.

4. **Deposits on Sieve Plates**: At the end of the growing season, certain substances can be deposited on these sieve plates. This deposition is a response to the aging of the sieve tubes and helps regulate the transport of sugars.

5. **Identifying the Correct Substance**: Among the options given (pre protein, callous, lignin, and ABA), the correct answer is **callous**. Callous is a substance that can be deposited on the sieve plates and plays a role in regulating the flow of sugars.

6. **Conclusion**: Therefore, the substance that gets deposited over the sieve plate in old sieve tubes at the end of the growing season to regulate sugar transport is **callous**.