Question

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

Answer 1

P-protein is also called phloem protein. If there is a disruption of the sieve element, P-protein aggregates at the sieve plate and prevents the leakage of phloem exudates. If there is an injury in the phloem, callose protein is deposited at the sieve plate.

Complete answer:
The p-proteins can be traced to the phloem. The most important function of P-protein is the Sealing mechanism on wounding. They generally play a role during an unfavorable condition where they quickly aggregate at the sieve plate to form a clot when the sieve element is disrupted. It prevents the flow of the phloem sap.

Additional Information: Phloem consists of many types of cells including sclerenchyma, parenchyma, sieve elements, and corresponding cells. The so-called "sieve part" can be more precisely referred to in angiosperms as a sieve tube member, and in gymnosperms and ferns as a sieve cell. Companion cells are the cells found in angiosperms with abundant plasma and nucleus.
In Gymnosperms, the phloem lacks both the sieve tube and the corresponding cells. Instead, they contain sieve cells for food material conduction.
The sieve element is the phloem conductive element. Companion Cells for the sieve function are "life support" cells. Fibers developed from sclerenchyma cells and provide the plant with structural support. Parenchyma serves as material for packaging between other types of cells and helps to move materials to the SE / CC complex.
So, the correct answer is ‘Sealing mechanism on wounding.’

Note: Gymnosperm sieve cells lack a sieve layer and instead have sieve pores across the cell wall that allow flow between adjacent cells. The members of the sieve tube found in flowering plants are typically larger than sieve cells and have sieve plates that link the ends of adjacent cells. These sieve plates are areas with several pores, from which a continuous cytoplasm connects adjacent cells.