Water Movement Up the Stem
Getting water from roots to leaves in tall plants requires three different mechanisms working together, each effective at different heights.
Capillary action works through adhesion between water molecules and the lignin lining of xylem vessels. This attraction helps pull water upward but only works effectively over short distances of about 5 centimetres.
Root pressure extends the reach up to 5 metres by using active transport in endodermis cells to maintain the mineral concentration gradient. This creates enough pressure to push water considerably higher than capillary action alone.
For the really impressive heights up to 100 metres, plants rely on transpiration pull. Water molecules stick together (cohesion), forming continuous columns in xylem vessels. When water evaporates from leaves, it literally pulls the entire column upward through this cohesion-tension mechanism.
Amazing Fact: The same cohesion-tension theory that moves water up 100-metre trees works in your garden plants too - it's just operating on a smaller scale!