How do Trees Lift Water From the Ground?

Handout 21 of Biology 101
Professor Mayim Etzman

 

  How do trees raise water from their roots to the leaves?  Trees have tall tiny diameter columns made of cellulose called xylem.  Water rises up the xylem by capillary action.  You can see these forces in action if you dip a paper towel in a bowel of water and watch the water rise up out of the bowl and up the paper towel.  Another force that raises water is solar radiation which vaporizes water inside leaves so that osmotic pressure pulls water into the leaves. This process is called transpiration. It's important to keep in mind that water is being pulled up to the top of the tree not pushed.  The redwood tree in the picture below is over 300 feet high.  It is truly remarkable that redwood trees can lift water so high.