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Water cannot be pulled up more than ( 10, 5, 20 )m, which is a problem tall trees must be overcome. Xylem vessels are very narrow, and water molecules tend to stick together because of the ( hydrogen, covalent, strong ) bonds between them - this property of water is called ( cohesion, tension ). As water moves out of the ( xylem, phloem ) in a leaf, it drags other molecules of water behind it. Because the vessels are so ( narrow, wide ), the column of water behind does not break, and water is pulled up all the way from the roots.
The pulling force is so great that the column of water is actually being ( stretched, pulled ) - it is under ( tension, cohesion ). The tension in the column of water tends to pull the walls of the vessels ( inwards, outwards ) slightly. However, the ( lignin, cellulose ) in the walls is strong enough to stop the vessels ( collapsing, bursting, breaking ).