AP BIOLOGY

Detailed explanation-1: -The unidirectional movement means the movement of molecules in only one direction. Xylem is unidirectional in terms of transportation, meaning the flow of water molecules takes place from the roots towards the top of the plant.

Detailed explanation-2: -The transport of water in the xylem takes place only from the roots to the leaves. Therefore, the movement of water and nutrients in the xylem is unidirectional.

Detailed explanation-3: -Xylem is unidirectional, whereas, phloem is bidirectional.

Detailed explanation-4: -Flow in Xylem is unidirectional while in Phloem is bidirectional.

Detailed explanation-5: -Reason: Movement of molecules inside xylem is unidirectional always upwards.