# Explain how the cohesive and adhesive properties of water are essential for its transport in the xylem of plants.

> IB DP Biology Higher Level (2023 syllabus) — A1.1 Water · Explain · 4 marks

## Mark scheme (4 marks)

1. Water molecules exhibit cohesion, meaning they are attracted to each other.
2. This cohesive force is due to the formation of hydrogen bonds between adjacent water molecules.
3. Water molecules also exhibit adhesion, forming attractions with the hydrophilic surfaces of the xylem vessel walls.
4. Together, cohesion and adhesion allow for the formation of a continuous column of water that can be pulled upwards by transpiration, resisting gravity.

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