Transpiration Pull Drives Water Uptake

Steps:

• Water evaporates from mesophyll cell walls in leaves, creating tension.
• This tension pulls water up through xylem vessels via cohesion between water molecules.
• The process, called transpiration, maintains continuous water column from roots to leaves.
• No energy input needed; it's passive, driven by evaporation.

Why C is correct:

• Transpiration is defined as evaporation from mesophyll cell walls, generating the cohesive tension that pulls water upward in xylem per the cohesion-tension theory.

Why the others are wrong:

• A: Active transport requires ATP and occurs in roots, not leaf epidermis for upward movement.
• B: Mesophyll "walls" is imprecise; evaporation specifically occurs from cell walls of mesophyll cells.
• D: Photosynthesis uses water but doesn't create the pull; it's a minor sink compared to evaporation.

Final answer: C