Re: Tree sap question


In article <478bs3pbfj9lq878n8gsuj49q50ei27u2f@xxxxxxx>,
®óñ© © ²°¹°-°² <ron@xxxxxxxxxxx> writes:
|>
|> >|> Then try Osmosis. It's very powerful, and not limited to 30'
|> >|>
|> >|> http://en.wikipedia.org/wiki/Osmosis
|> >
|> >An old and good physical rule is that, if your explanation allows
|> >you to construct a perpetual motion machine, your explanation is
|> >wrong.
|> >
|> >Osmosis still requires energy to drive it.
|>
|> Osmosis is not perpetual motion. The attractant is fuelled by our
|> beneficent sun.

That is an evasion. Osmosis requires a concentration gradient or
similar, and causes a pressure differential. A reduction cannot
raise water by more than 30' and all of the books indicate that the
maximum actual excess pressure is nothing like the 1 MPa per 30m
needed. Good try, but no banana.

It would be easy if plants had anything like venous return valves,
to act as a pump, but they don't.

The question remains is HOW does the sun's radiation get transferred
into the movement of the water? And I believe that is unknown.


Regards,
Nick Maclaren.
.

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