Tuesday, 26 September 2017

botany - How do trees lift water higher than 10 meters?


The atmosphere pressure is 10 meters of water (approx). This means that it is impossible to lift water higher than 10 meters with vacuum or сapillary action (on Earth, under normal conditions).


There are trees higher than 10 meters.


How do they lift water to their tops?


UPDATE


In other words: how cohesion-tension theory can be true if it apparently contradicts the laws of physics?


UPDATE 2


Atmospheric pressure helps to rise the water, not resists rising. What is resisting is water weight. When water column is 10 meters high, then atmospheric pressure can't help anymore.


Any adhesion/cohesion mechanism can't help here too, because it acts only in thin molecular layer. To transfer action force further the pressure is required, which is insufficient at 10 meters.



UPDATE 3


If we had capillary small enough to rise water to 10 meters and then we will build smaller capillary which we expect will rise water higher, we will fail. Water column will break and does not climb higher than 10 meters.


enter image description here


Menisci acts like small piston and can't help rising water higher than 10 meters.


UPDATE 4


Common pressure distribution in capillary is follows:


enter image description here


$P_0$ is atmospheric pressure. As you see, right under menisci, the pressure is lowered by $2 \sigma / R$ where $R$ is the radius of menisci and $\sigma$ is surface tension. The entire term is called "Laplace pressure". As you see, it can't supersede atmospheric pressure, because water continuity will be broken in the case.


I.e. no any menisci can rise water higher than 10 meters.


The existence of higher trees PROVES that there are some other significant mechanisms, not adhesion/cohesion, not capillary.



UPDATE 5


Current version, as I understood it, is based on a declaration, that a water, if put into thin capillary, can behave like a solid body. Particularly, it can resist tension up to minus 15 atmospheres.


This is a tensile strength of concrete, so I don't believe that without additional proofs.


I think it is just not hard to make thin tube, put water into it and check, how high it can climb.


Was it done ever?




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