In botany, are the primary conducting elements of the phloem tissue in flowering plants (angiosperms). They are responsible for translocation , the transport of organic nutrients (like sucrose) from the leaves to the rest of the plant.
: Lubricated by a clear, slippery fluid produced by the bulbourethral glands (Cowper's glands) to protect and ease the passage of fluids.
: They are formed by joining individual cells called sieve tube elements end-to-end to create a continuous pathway.
: Because they lack a nucleus, mature sieve tubes rely on companion cells for metabolic support and life-sustaining functions. 2. Slipperiness in Other Biological Tubes