The upward movement of water more than 100 meters in a redwood or eucalyptus (there is a traditional dispute between Americans and Australians over who has the tallest trees!) seems to be a gravity-defying task of epic proportions. Gravity is certainly a factor, and ultimately limits how tall a tree can get, but there are other forces at work that can meet that challenge. The amazing thing about plants is that the process is largely passive, in the sense that plants expend practically no energy to accomplish it. There are no muscles and no heart in a tree to pump water upward. What there is, is basically a gigantic paper towel.
|The water molecule (A) consists of a negatively charged oxygen atom and two positively charged hydrogen atoms. This causes them to stick together in chains (B) and to the walls of cellulose fibers (C).|