Which plant tissue is primarily responsible for transport of sugars from leaves to other parts of the plant?

• A. Xylem
• B. Cortex
• C. Epidermis
• D. Phloem

Answer: (D)

Sugars produced in leaves are transported by the phloem to other parts of the plant. Phloem moves photosynthates, mainly sucrose, from sources like mature leaves to sinks such as growing tissues and storage organs. This occurs via the pressure-flow mechanism: sugars are actively loaded into sieve tube elements in the source, lowering water potential; water moves in from the xylem, generating positive turgor pressure that pushes the sap through the phloem toward where it’s needed. At the sink, sugars are unloaded for use or storage, and water exits, continuing the cycle. Phloem, made up of sieve tube elements and companion cells, is specialized for this long-distance transport, whereas xylem carries water and minerals upward, and cortex or epidermis serve other roles.