How does water really reach the leaves of trees?

Andrew Kenneth Fletcher gravitystudy at hotmail.com
Tue Feb 29 13:24:06 EST 2000


Hi Mathew

I included the text from GCSE Biol in order to illustrate accepted theory.
If we make this too complicated from the onset, it is more likely to be
missed or skipped.

Would you be so kind as to sum-up the cohesion-tension theory for people who
may want to follow this thread.

I have an interesting theory of my own about the way trees and plants lift
water. It also relies on some aspects of cohesion.

The theory is very simple. Evaporation from the leaves, concentrates the
liquid in the leaf. Gravity then pulls the concentrated liquid down the
tree, which in turn draws more dilute sap up the tree.
This simple flow and return system, is an inevitable consequence of what is
in effect, distilled water leaving a liquid which contains minerals, or
anything that is heavier than water.


Matthew J. Linton <linton at botany.uga.edu> wrote in message
news:89gli8$5n9$1 at cronkite.cc.uga.edu...
> If you find that "the accepted explanations for fluid transport [are]
> somewhat confusing," perhaps you should do additional reading in the
field.
> The theory of water transport, which is called "the cohesion-tension
> theory," is well described in a number of textbooks, the best of which
might
> be "Plant Physiology" by Frank B. Salisbury and Cleon W. Ross.  Your local
> college or university library probably has a copy of it.  The text that
you
> included is VERY POOR at describing xylem and phloem transport, osmosis,
and
> root pressure.  There are alternative theories for water transport,
notably
> one by M.J. Canny 1995 "NEW THEORY FOR THE ASCENT OF SAP-COHESION
SUPPORTED
> BY TISSUE PRESSURE" Annals Of Botany 75(4):343-357, but this theory really
> hasn't survived a number of follow-up research studies, including articles
> in Nature (378:715-716) and Science (270: 1193-1194).  Although it is
> healthy for one to question established theories in science, you can't
just
> disregard decades and decades of careful research by hundreds of
scientists
> just because "the accepted explanations...are somewhat confusing."
> Good luck in your quest.
>
> Matthew J. Linton
>
>





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