Rays are channels of cells where water, nutrients and carbohydrates move laterally. What term describes these channels?

• A. Xylem
• B. Phloem
• C. Cambium
• D. Rays

Answer: (D)

Rays are radial rows of living parenchyma cells that run through wood from the inner to the outer tissues. They provide lateral, or horizontal, pathways for moving water, nutrients, and carbohydrates across the stem, connecting the xylem and phloem and linking storage areas with transport tissues. This lateral transport complements the vertical conduction that xylem and phloem handle. Cambium is the growth layer that generates xylem and phloem, not a sideways conduit. So, when describing channels that move substances laterally, the term that fits is rays.