In sapwood, the pathways for food movement to and from the phloem are called?

• A. Xylem rays
• B. Sapwood
• C. Heartwood
• D. Growth rings

Answer: (B)

Food movement between the phloem and the rest of the plant takes place through the living, conducting tissue in the outer xylem—the sapwood. Sapwood contains living parenchyma cells and rays that enable lateral exchange and transport of nutrients (the sugars produced in leaves) to the phloem and back. Heartwood, in contrast, is dead and no longer participates in transport, and growth rings are simply yearly structural features. While the actual channels for horizontal movement exist within the xylem rays, the region that supports and enables this exchange is the sapwood. Therefore, sapwood is the best answer.