Radial transport refers to which movement?

• A. Horizontal movement of water or nutrients between cells through ray cells
• B. Upward movement of water
• C. Phloem loading
• D. Lateral movement of water through bark

Answer: (A)

Radial transport is the movement across the radius of a plant organ, i.e., lateral movement through tissues from one side to the other. In woody plants, ray cells are radial parenchyma cells that extend from the center outward and connect xylem and phloem. They provide pathways for water, minerals, and sugars to move sideways between tissues, redistribute resources, and support storage and repair. This direction of movement contrasts with vertical upward water transport in the xylem (driven by transpiration) or processes like phloem loading (which is about getting sugars into the phloem from sources). So the concept describes the horizontal, cross-tissue exchange through ray cells.