In the sieve elements, which one of the following is the most...

Sieve elements are a component of phloem tissue and are responsible for conduction of food in plants. A sieve tube element has peripheral layer of cytoplasm without any nucleus. The central part is occupied by a network of canals which contain fibrils of $p$-protein. The protein is vibratite and is believed to actively participate in the transport of nutrients. One general property of its ability to form a gel and it functions as a puncture repair substance forming a plug at any site of damage in sieve element, thus preventing loss of food materials being translocated by the phloem. Thus it is believed to have sealing function on wounding.