A full discussion on this topic can be found on the link above at the Naked Scientists Website.
The arguments for accepted explanations for fluid transport in trees has not been forthcoming, in fact this thread has shown they are indeed flawed.
Ever thought about how Giant Trees towering over a hundred metres can raise water to their leaves without an obvious pumping mechanism?
It may interest you to know that the current explanations are nonsense.
Take root pressure for example. Do roots really squeeze water to the tops of trees? "of course not." Or does capillary action cause trees to soak up water like a sponge to over 100 meteres and release it into the atmosphere?. "impossible!" If this was the case, rising damp would ooze from the tops of walls and even tall buildings? The Oceans would infiltrate the soils and ooze out at a higher level than the ocean.
The Cohesion tension theory as it stands sucks! And relies on water leaving the leaves and this is thought to somehow drag on a chain of water stretching right to the roots. (elaborate way of saying it sucks)
Imagine standing on a desk let alone a hundred meters in the air and trying to suck water up a straw from a bottle on the ground. We can't do it so why do we expect a tree to be given different rules? It goes on to say that the huge number of leaves cause a collective pull. Well there are plenty of trees that stand at impressive heights, that are not furnished with a huge canopy of leaves and yet are able to effortlessly draw water from the soil and absorb moisture from the air. The larch being one example. But what about deciduous trees. In the Autumn the leaves fall and yet somehow in the spring the tree picks up where it left off and circulation continues inside causing the buds to form. How does this fit with the leaves having to pull water up? And then Straburger’s experiments where he killed a tree suspended vertically in a bath of picric acid. Strasburger observed circulation continuing for several weeks after the tree was completely killed ruling out living processes.
For those out there that continue to adhere to these quaint proposals for the ascent of sap in tall trees, namely root pressure, the cohesion tension theory, osmosis, capillary action, They are WRONG!
The trees circulate fluids, they do not have a preposterous one way fluid hoist system!
They do however circulate sap, driven by density changes caused by evaporation altering the density of sap within the leaves and branches not unlike our own circulation which also benefits from density changes in the fluids again caused by evaporation.
Andrew K Fletcher