Einstein Science Reporting for Kids
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22-Dec-2005

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American Association for the Advancement of Science

Water in the trunk of a tree



Click here for a high resolution photograph.

Every December, people cut down pine trees and other evergreens and stick them in their houses. The trees start sucking up water right away (unless you wait too long between cutting the tree and putting it in water, of course). A new study helps to explain how the heck water moves up the trunk of cone-making trees called "conifers."

Scientists who are into dissecting and studying trees have long known that water moving up the trunk of a pine tree, or other conifer, has to pass through many more "blockades" than water moving up the trunk of an oak tree, or other "angiosperms" tree.

These partial blockades or "valves" in trunks and branches of trees connect one water-carrying tube to the next.

For the first time, scientists have measured just how hard it is for water to move through the individual valves of pines and other cone-making trees.

They found that it is much easer for water to move through the valves of pine trees than oak trees and other angiosperms. This explains why water seems to move just about as easily up the trunk of a pine as an oak, even though the water has to move through more valves in the branches of a pine than an oak.

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This work from Jarmila Pittermann and colleagues from the University of Utah in Salt Lake City, Utah appears in the 23 December 2005 issue of the journal Science.