The sieve tube elements are specialized elongated cells in the phloem that connect end to end forming a tube. The main function of this tube is to transport nutrition in the form of carbohydrates. Sieve cells have no nucleus, ribosomes and cytoplasm, meanin they cannot carry out primary metabolic activities. The companion cells, which are closely associated with the sieve tube elements, carry out the their metabolic functions.

sieve tube.

1. Sieve tube elements contain little cytoplasm and no nucleus
2. Has cross walls with pores to allow flow of sap
3. Companion cells on the side that have mitochondria to produce ATP for active processes
4. Companion cell and sieve tube element are linked through many plasmodesmata

In plant anatomy, sieve tube elements, are a specialized type of elongated cell in the phloem tissue of flowering plants. The ends of these cells connect with other sieve tube members, making up the sieve tube, whose main function is transport of carbohydrates in the plant.

In plant anatomy, sieve tube elements, are a specialized type of elongated cell in the phloem tissue of flowering plants. The ends of these cells connect with other sieve tube members, making up the sieve tube, whose main function is transport of carbohydrates in the plant.