How do Trees Really lift Water to their Leaves?

Rosy:
1. Yes, no-one said different.
2. Well, sort-of. "Sap" doesn't just move in and out of leaves like fluids round your plastic-tube experiments, it has to undergo transport across cell membranes. Apart from that, yes, denser liquids (on average) move down, and are replaced by less dense liquids.
3. No. I wouldn't expect the salts and sugars to remain in the leaf. This is a total straw man and you are avoiding doing the maths.

Our problem with your theory, as I have explained at length elsewhere, is that you have not accounted for sufficient energy being available to the system to lift the amount of water you're claiming it must lift. Since you've been expounding this theory, on this thread, for four-and-a-half years now, this is an extraordinary omission and, frankly, seems to me to justify BC's inclination to characterise you as a troll. My own assessment runs more to "faith nutter" but the two are not mutually exclusive (troll need not always, after all, imply malice).

And I have stated many times that the density change in the phloem sap gives the xylem an increased head or in simple terms raises it above the level of the phloem. Sophiecentaur related this to how locks between saline and fresh water show the different levels.

Therefore as the tree grows right from a seed, the dilute sap pushed higher and higher, as the phloem continues to support the less dense sap at a higher elevation than the falling sap, of course the tree does not directly afford the increased head of water but the pressure differences albeit minor affords the tree a direction to grow in with ease.

This is shown clearly in the video link provided using a water filled U tube. The density difference shows clearly the change in water levels.

How do you suggest we account for this in maths?

Rosy:
OK. This is what we mean:

You can calculate (easy physics) the energy required to raise a certain mass through a given distance (E=mgh, energy in joules = mass in kg x g x height in metres where g acceleration due to gravity and is 9.831 metres per second per second)

So to raise 1 kg by 1 metre using gravity, you must lower 1 kg by 1 metre to balance it (or 2 kg by 0.5 m or 0.5 kg by 2 m).

Your claim that gravity can drive the transport of fluids in plants therefore demands that to move 1 kg of water from the roots to the leaves, you must lower 1kg of something-or-other.
Some of that will be water, but if we assume that 90% of the water taken up by the roots is lost in transpiration*, that means that for every 1 kg of water that moves up the tree, 900 g of sugars (principally sugars, as most salts and nitrogen containing compounds have to come up from the roots in the first place) must be produced and moved down**.

Infact, crops transpire*** between 200 and 1000 kg of water for every 1 kg of dry mass (sugars plus all the other stuff) they produce.

If we could get that sort of biomass production out of trees there'd be much less call to be worrying about fossil fuels!!

OK, there's my first stab at the numbers. Can you point out how your system gets passed this apparently insurmountable energy barrier? Or not?


*(I got the figure off wikipedia, but it's a reasonable number and is something that's been measured lots of times)

**(even without accounting for the fact that water is used in sugar synthesis and making 900g of sugar would use of the order of 450 g of water)

***(again from wikipedia)

BC:
"1. Yes, no-one said different."

Well, actually I did say differently.

You start with a gram of sap. It loses a tenth of a gram of water by transpiration and gains a tenth of a gram of water drawn up from the roots.
You have exactly the same thing as you started with so the density is the same as it was.

Anyway, since Andrew is quite passionate in his refusal to even try to show us some numbers I think it's fair to assume that he knows that wouldn't support his point of view.
Until I see him prove otherwise I don't see anything changing my opinion on the matter.

Rosy:

Yeah, alright BC, you have a point. Sorry.

I think there's a (very sloppy) argument (or isn't there?) that some of the water drawn up the xylem (as part of a less-dense) solution then becomes part of a (more dense) solution in the phloem, so in that sense a solution gains density (if you ignore the whole transport into/out of cells thing that has to happen at the top, which you can't really).

And you're probably right about Andrew too, not sure why I bother... but somehow I keep on coming back in the hope some day he'll catch on.

I keep coming back also in the hope that someday you will all catch on!

Those pictures of varicose veins resolving by tilting a bed the opposite way to that recommended by the medical profession is not unrelated to this discovery as has been suggested in the past.

I tilted the bed in the first place to test if a flow and return in the body was present. If it was then a swollen vein would reduce in size. Precisely what happened and is happening to many people.

Yet conveniently ignored by people who should know better!

Very difficult to ask a tree if gravity is having an affect. But very easy to ask a person to lay on an angle and observe the changes!

You may not like the fact that someone outside of academia has delivered a profound discovery and frankly I couldn’t give two hoots what belief based system you adhere to.

The experiments shown on Youtube speak volumes more than an imagined impossible leaf based pull on a 100 plus meter Californian Redwood.

Show me the numbers that support this absurd belief?

Better still take a look at what the students think about it: www.thestudentroom.co.uk/showthread.php?t=599353

The cohesion tension hypothesis relies on a continuous bead of water to support a column and the evaporation at the top of the column can not only support the fluid but can pull it up the trunk and release it into the air.

But we know that cavitation takes place all of the time and that any break in the bead of the imagined cohesion tension generated by a flimsy leaf flapping around in the breeze would render the whole process redundant. Yet the tree appears to not be affected by the constant cavitations, which can be heard cracking with a standard stethoscope. But that’s accepted and to be expected in a belief -based system.

You can’t ignore this fact!


The following relates to the cohesion tension hypothesis.
4e.plantphys.net/article.php?ch=&id=99

Rosy:
Andrew

If you got over your puerile inverse-snobbery for just long enough to give our criticisms of your system serious consideration, you would do one of two things. Either you would strengthen your argument immeasurably, or alternatively (and I grant you I think it's more likely), you'd realise that your model is untenable and be able to go away and refine it/not spend the rest of your life beating your head against the internet.

If you don't address this very specific question, you will be a fool in ways that have nothing to do with academic qualifications one way or another, but everything to do with blind arrogance.

But we know that cavitation takes place all of the time and that any break in the bead of the imagined cohesion tension generated by a flimsy leaf flapping around in the breeze would render the whole process redundant. Yet the tree appears to not be affected by the constant cavitations, which can be heard cracking with a standard stethoscope. But that’s accepted and to be expected in a belief -based system.

Bunk. Trees grow outward, too, you know. They grow new xylem and phloem tissue which is filled with fluid as the cells grow. Sure some of them break, that's why new ones are required.
Plus of course you've shown (bully for you) that even with an enormous diameter tube (relative to a xylem) it is perfectly possible to raise a column of water above 10 m (not an equilibrium system, but then life has very few equilibrium systems), and given a much finer column and therefore very different surface behaviour between the xylem fluid and the inner surface of the xylem, your "argument from incredulity" doesn't wash there.

Just because you don't believe it can happen, doesn't mean it doesn't.
On the other hand if the energy accounting doesn't work out you better have a pretty damn good explanation because you've just declared all trees to be perpetual motion machines on a grand scale.

Your inclined bed theory has nothing to do with trees and might stand a better chance of not "being ignored by people who should know better" if you made at least some effort not to come across as a fool. After all, the first google result for "Andrew K Fletcher" (and therefore the first thing someone wanting to find out more about this person who's sent them information about his new theory for solving all of medicine), is your Naked Scientist Forum profile. Which will bring them straight here. The majority of people in the category of "people who should know better" are likely to feel much as I do about your total refusal to interact with our very specific criticisms of your pet theory.

The cavitations repair themselves, cavitations are taking place all of the time and emit loud cracking sounds. This does not result in the collapse of the circulation in the tree and this is where the problem with the cohesion tension hypothesis lies.

Have you any idea of how much pressure would be required to support the columns of water in tall trees using the cohesion T model? Do you not think that the leaves would literally become inverted under such immense tension or even sucked down the trees vessels for that matter?

Pete Scholander and Ted Hammel hit the nail on the head when they made the pressure bomb and began recording pressures far above those proposed and required by the CTT.

So ask yourself if this imaginary impressive tension is not present in tall trees how on earth are they able to conform with the rest of the theory?

Can you not see how absurd it is to propose that leaves can suck up water from the roots no matter how it is wrapped up?

@BenV
Ben let us look at those maths in the Cohesion tension hypothesis first.
4e.plantphys.net/article.php?ch=&id=99
The application of the Ohm′s law to sap flow encompasses many phenomena (heat transfer, water transfer in soil, Darcy law, first diffusion law, etc.) and, it is therefore independent of the underlying physical mechanisms and the nature of moving fluid. For example, the electrical approach does not address whether sap is under tension or pressure. For this reason, the description of sap flow by Ohm′s is rather "phenomenological".

Had to look this word up: en.wikipedia.org/wiki/Phenomenology_%28science%29
Phenomenology in physical sciences

There are cases in physics when it is not possible to derive a theory for describing observed results from the known first principles (such as Newton's laws of motion or Maxwell's equations of electromagnetism). There may be several reasons for this. For example, the underlying theory is not yet discovered, or the mathematics to describe the observations is too complex. In these cases sometimes simple algebraic expressions may be used to model the observations or experimental results. The algebraic model is then used to make predictions about the results of other observations or experiments. If the predictions made by the algebraic model are sufficiently accurate, they are often adopted by the scientific community despite the fact that the algebraic expressions themselves cannot be (or have not yet been) derived from the fundamental theory of that domain of knowledge.

The boundaries between theory and phenomenology, and between phenomenology and experiment, are fuzzy. Some philosophers of science, and in particular Nancy Cartwright argue that any fundamental laws of Nature are merely phenomenological generalizations.