> These vessels have evolved intricate adaptations that can maintain the water in liquid form, even under the extreme low pressures This sentence undersells th

> These vessels have evolved intricate adaptations that can maintain the water in liquid form, even under the extreme low pressures This sentence undersells the phenomenon quite a bit: the “extreme low pressure” is in fact several bars of negative pressure and the challenge of maintaining water in liquid form is avoiding cavitation. I was exposed to the physics of trees though the entrance exam to École Polytechnique (France's best University) and it's been carved in my mind since then: http://alainrobichon.free.fr/Concours/X_PC_PH1_01.pdf http://alainrobichon.free.fr/Concours/X_PC_PH1_01.pdf AFAIK students are still being given this masterpiece for practice even though it's now 25 years old.