Sieve tube

The sieve-tube members are cells that lack a nucleus, have very few vacuoles, and contain other organelles such as ribosomes. The endoplasmic reticulum is concetrated at the lateral walls. The survival of sieve-tube members depends on a close association with companion cells. Sieve tube members are joined end to end to form a tube that conducts food materials throughout the plant. The end walls of these cells have many small pores and are called sieve plates and have enlarged plasmodesmata.