In the sieve elements, which one of the following is the most likely function of P-protein-
(a) Autolytic enzymes
(b) Sealing mechanism on wounding
(c) Providing energy of active translocation
(d) Deposition of callose on sieve plates

Options

A. Autolytic enzymes
B. Sealing mechanism on wounding
C. Providing enerfy of active translocation
D. Deposition of callose on sieve plates

Answer

To determine the most likely function of P-protein in sieve elements, let's analyze the options provided:

1. **Understanding P-proteins**: P-proteins are proteins found in the phloem of flowering plants. They play a significant role during unfavorable conditions, particularly when the sieve elements are disrupted.

2. **Evaluating the options**:
- **(a) Autolytic enzymes**: P-proteins do not function as autolytic enzymes. Their primary role is not to break down cellular components.
- **(b) Sealing mechanism on wounding**: P-proteins aggregate at the sieve plates when there is damage or wounding. This aggregation forms a clot that helps seal the wound and prevents the loss of phloem sap.
- **(c) Providing energy of active translocation**: The energy required for active translocation in plants is provided by ATP, not P-proteins.
- **(d) Deposition of callose on sieve plates**: While callose is involved in sealing, it is not the primary function of P-proteins. P-proteins are more directly involved in the immediate response to wounding.

3. **Conclusion**: Based on the analysis, the most likely function of P-protein is **(b) sealing mechanism on wounding**. They aggregate and form a clot to prevent the loss of phloem sap during times of injury.

### Step-by-step Solution:
1. Identify the role of P-proteins in the phloem.
2. Analyze each option provided in the question.
3. Eliminate options that do not align with the known functions of P-proteins.
4. Conclude that the correct answer is (b) sealing mechanism on wounding.