While capillarity contributes to the initial rise of water in the narrow xylem vessels of plants, the primary force responsible for lifting water to significant heights (especially in tall trees) is transpiration pull. Transpiration (evaporation of water from leaves) creates a negative pressure (tension) that pulls the continuous column of water up the xylem vessels, aided by the cohesive forces between water molecules and adhesive forces between water and xylem walls.
For which one of the following is capillarity not the only reason?
Asked in UPPCS Prelims 1999 · Topic: Physical Properties of Materials (Viscosity and Surface Tension)
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Answer: D. Rising of water from the roots of a plant to its foliage
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