Water travels from the roots of a tall tree to its leaves through narrow xylem tubes, with no pump pushing it. Which pairing of water properties best explains how an unbroken water column is pulled upward?

Core Concept

Evaporation from the leaves generates negative pressure that pulls the whole column of water upward. Cohesion, produced by hydrogen bonding between neighboring water molecules, keeps that column continuous so it can be pulled like a rope instead of snapping apart. Adhesion lets water hydrogen-bond to the polar cellulose of the xylem walls, resisting the downward pull of gravity and stabilizing the column. Together these forces form the cohesion-tension mechanism that lifts water many meters without any energy input from the plant. Specific heat concerns temperature buffering, hydrophobic effects build membranes, and dissolved ions ride along without providing the pull.