A column of water within xylem vessels of tall trees does not break under its weight because of
1. Dissolved sugar in water
2. Tensile strength of water
3. Lignification of xylem vessels
4. Positive root pressure

Xylem transports air by:
1. the proton pump
2. active transport
3. chemiosmosis
4. air is not transported by xylem normally

In the cohesion-tension-transpiration pull model, the upward pull of water is transmitted to other water molecules by cohesion which is caused by: