Xylem · Botany

What provides the driving force for the movement of water through the xylem according to the Cohesion-Tension theory?

  1. Active transport by parenchyma
  2. Root pressure only
  3. Gravity
  4. Transpiration pull
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Correct answer: Transpiration pull

The evaporation of water from leaves (transpiration) creates a negative pressure or 'pull.' Because water molecules are cohesive, this tension is transmitted down through the xylem, pulling water up from the roots.

Difficulty: Medium Question 19 of 20

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