In
plant anatomy,
sieve tube elements, also called
sieve tube members, are a specialised type of elongated cell in the
phloem tissue of
flowering plants. The ends of these cells are connected with other sieve tube members, and together they constitute the
sieve tube. The main function of the sieve tube is transport of
carbohydrates, primarily
sucrose, in the plant (e.g., from the leaves to the
fruits and
roots). Unlike the water-conducting
xylem vessel elements that are dead when mature, sieve elements are living cells. They are unique in lacking a nucleus at maturity.