Physics Dept Seminar

June 11th, Thursday (*SPECIAL DAY*)

How Trees Pull Water without Breaking It

Dr. Matej Kanduc

Dept. of Theoretical Physics, Jozef Stefan Institute, Slovenia

(Bio/Materials Phys., Host: Dias)

Room: ECE 202

Time: 11:45 am - 12:45 pm with 11:30 am teatime

It may seem surprising that we can lower the pressure in a liquid to negative values, far below the saturated vapor pressure at which a vapor phase should form. In water, such deeply metastable states are possible only when it is exceptionally pure and free of nucleation sites. It is therefore even more striking that plants transport water at negative pressures down to -100 atm without cavitation, even though xylem sap is anything but pure: it contains dissolved ions, sugars, lipids, and other organic molecules. How is this possible?

In this talk, I will show how molecular simulations and theory can explain this surprising behavior. We find that amphiphilic molecules such as lipids can adsorb onto hydrophobic surface crevices - places that would normally trap nanobubbles. Once coated, these surface defects can no longer stabilize bubbles, which allows water to stay intact even under strong tension. This mechanism offers a molecular-level explanation for how trees transport water to heights of over 100 meters without cavitation. More broadly, it illustrates how soft-matter physics and interfacial molecular organization can control the mechanical stability of liquids under extreme conditions.