03 January 2015

Negative pressure in the xylem tubes of trees

"Trees create immense negative pressures of 10's of atmospheres by evaporating water from nanoscale pores, sucking water up 100m in a state where it should be boiling but can't because the perfect xylem tubes contain no air bubbles, just so that most of it can evaporate in the process of absorbing a couple molecules of carbon dioxide."
I can't quite wrap my mind around the concept of such immensely negative pressures inside trees, but then I was an English major...

A tip of the blogging hat to reader Dan Noland, who found the video.


  1. Replies
    1. Wow, didn't realize how unusual it was till I read this!

  2. The forces involved here had convinced many early natural philosophers that "vitalism" was real, otherwise this would be impossible


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