P-protein aggregates at the sieve plate when the sieve element is disrupted, preventing the passage of phloem exudates.
The sap-conducting sieve components of phloem tissue in plants contain substantial levels of P-protein (phloem protein).
Its capacity to form a gel serves as a puncture repair substance, producing a plug at any location of damage in the sieve element and preventing food materials from being translocated by the phloem from being lost.
The P-protein is mostly found lining the interior wall of a fully functional sieve element.