"Martin" wrote in message
...
On Fri, 13 Aug 2004 16:58:48 +0000 (UTC), "Franz Heymann"
wrote:


"Tim Challenger" wrote in message
...

I doubt if any metabolites are involved in the transport of
water
to
the leaves. Surely osmotic pressure is enough to do the job?

Osmotic pressure does the job of course to a certain extent and
for
short
plants this is normally enough, but *water tension* is another
major
factor*.

I have my doubts. I have never heard a convincing explanation of
that
concept.
On the other hand, I know that sea water is rather more
concentrated
than the sap in a plant, and I do remember that the osmotic
pressure
of seawater

21.5 atmospheres
http://dbhs.wvusd.k12.ca.us/webdocs/...-Equation.html

is enough to raise a column of sea-water to a height of
more than 700 feet.

688 feet?

I had the dead sea in mind. {:-))

Franz