Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: scientizscht on 29/09/2019 23:13:24
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Hello!
It is known that trees lift relatively significant amounts of water at significant heights using their capillaries. The capillaries get 'wet' and this makes the water reach the leaves at height where I assume the water is consumed by the cells of the leaves.
If we isolate the system, we have at the beginning water in the ground and after some time when the capillaries act, we have water at height where it then enters the cells of the leaves.
There is clearly energy consumed to lift all that water to all that height and this happens continuously as the water gets consumed at the top.
Where does this energy come from and how does the energy conservation apply?
Thanks!
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The sun.
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A sponge separated from water is in a higher energy state than a wet one, so the sponge will pull up water at least as far as the difference in energy. The capillary action of trees optimizes this distance, but it still only works so far, limiting the height of any plant.
At the top, some evaporates. Water separated from low humidity air is again in a higher energy state than water evaporated into that air, so it flows without energy input.
Plants consume water in their photosynthesis reactions, and that results in a higher, not lower, energy state. So energy must be input for that step, and that energy indeed comes from solar radiation.