How do Trees Really lift Water to their Leaves?

Water is inside the tree during growth and the tree does not have to lift water to it's leaves because it is already at the leaf and if it is not then the leaf is desiccated and dies! No need to explain how a dead tree can suddenly decide it wants to pull water from the ground because it does not happen in nature. “Having said that I remember a Yucca Plant that died below completely yet somehow sent down a taproot through the dead trunk and began growing again.”

So if the fluids are suspended from ground level, all we need to show is how these fluids circulate by introducing a density pumping mechanism.

Here we have a density change caused by evaporation , which no one can argue against!

As molecules of denser solution are acted upon by gravity they have to migrate down the tree from a source to a sink and in doing so drag on all of the other sap molecules inducing not only a downward flow but a return flow. “for every action there is a reaction” The downward flow “source to sink” in a tree is located in the phloem. The sap in the phloem contains more dissolved solutes and is denser than the upward flowing xylem sap. If you can for a minute picture the beads of phloem sap as links in a chain around the branches and trunk of a tree it is not difficult to see how phloem in some parts of the tree can move against gravity as it is dragged around the circuit by the downward flowing denser sap.

We don’t need to show buckets with stones in them and rope as an analogy, it simply does not fit with the fluid model because the fluid model adapts to suit the different diameters of tubular cells within a tree.
I have mentioned before that the density changes in the ocean caused by evaporation and heat drive the Altlantic Conveyor System, an underwater river bigger than all the rivers in the World put together. In the ocean there are no vessels or tubular cells to obscure the density bulk flow.

In a domestic pump-less hot water system we can see a flow and return “copper pipes” This appears to behave the same as the ocean and does not rely on nylon as a material as you suggested earlier.

INDEED WHY WOULD WE EXPECT THE SAP IN A TREE TO BEHAVE DIFFERENTLY?

Your rope analogy cannot adapt or alter it’s shape, it is after all a solid, so for example as it passes over the pulley it would have to become thinner having shed some rope to the atmosphere and as you rightly state would counterbalance any added density. “your rocks in a bucket”.

When density changes in sap, it exerts a dragging effect on the molecules while at the same time exerts a positive pressure on the molecules in front of it. This positive pressure forces the more dilute xylem sap to move upwards above the original level adding the impetus for the tree to continue to grow vertically. It also explains as I have said before how sap exudes from a cut stem, nothing to do with root pressure but to do again with density changes in the sap!

Here is another analogy. Instead of rope we use stretchy slime. The slime can evaporate water to the atmosphere and become denser. The denser slime bulges as dissolved salts apply positive pressure to the slime causing it to visibly swell, (observed using latex soft walled tubing) and the upward flowing stretchy slime can be drawn up from a reservoir of slime under tension applied by the downward flowing slime causing it to become thinner (again observed in soft walled tubing). But the tree has the equivalent of a fluid filled support stocking “The Bark” that not only prevents the sap from bulging but prevents the internal cells from changing shape-due to the pressures applied internally. Very much like the pressure we apply to varicose veins and oedema using the stockings.

Trees grow and die perpetually or am I mistaken?

Witsend:

Hi Andrew. I'm not in the habit of agreeing with Sophiecentaur - but I must here make an exception. He's drawn an analogy to buckets and stones? Where is your answer? Alternate science is absolutely the very best of all things. In principle I am full blown, heart felt, initiate. But I draw the line when alternate science also becomes illogical.

Page one of this thread contains a reference to our understanding of osmosis by the now late professor H.T.Hammel, Emeritus Professor of the Max Plank Institute and a life,s work into the ascent of sap in tall trees, many published papers and he was definately not convinced by osmosis explaining everything or indeed anything in it's curent format.

Logic must also apply to the curent explanations for the ascent of sap in tall trees, but alas is clearly lacking in logic. For example: the evaporation of water from the leaves cannot suck / drag / move / pull / call it what you like on a column of water in a tall tree! We cannot suck water up more than 10 meters in an open ended tube, many people have tried over the years and failed so why should a tree have different rules?

Ok Andrew K Fletcher - I take it back. That was really well explained. It's more or less what I understood as the action of osmosis. Just couldn't think that it could be improved on or even that it should be questioned.

Clearly there's some nicety that eludes me.

Thanks for the explanation. I now need to understand why Sophiecentaur objects. It's possibly because you aren't qualified? That's why he won't answer my questions. Just tells me to get an eduction. I think we've been joined in the same bracket.

Incidentally I love your quote that you include in every post. I can't get an experiment replicated - and I know a little about that contempt.

Unless it's supposed to be the 'flow' that sustains the flow - being perpetual motion. Sophiecentaur

I think the point is that the sap from the phloem is not the same as the sap from the xylum. The actual sap is different, therefore their molecules are also different.

Here's my take, for what it's worth. The trees' roots are only able to take water in. They do not transpire. So once in it never comes out. That's simple osmosis. I remember it was described as a valve action that closed as the cells became turgid. So it's a one way action. The water is transported from the roots to the the xylum and then up the tree trunk in a sponge action. That precludes a pump action and the question then is how far is the reasonable for water to reach from a sucking rather than a pump action? I know damp rises.

It then reaches the leaves where it is taken into the leaf cells through that same osmotic action. There it is changed into sugar through the miracle of photosynthesis which then is ready to be transferred to various parts of the tree for it's general well-being. Then, having been manufactured the same sugary sap is fed back to the phloem cells in the stem of the leaves - as opposed to the xylum cells at its centre. Excess water is transpired from the leaves as a waste product of photosynthesis, together with oxygen, and the cells, through osmosis take in more water from the xylum cells to replace that lost in transpiration- and on and on. The action is, indeed, perpetual. But only in the same way as our own digestive system is pretty well perpetual. But I'm not sure that it needs anything more complicated than the xylum's ability to hold water - much as a sponge would hold water.

If I've missed the point - apologies.

Lyner:
AKF
You do not seem to understand so much of the Science I quote to you that really cannot rely on your having understood what you have read of H.T.Hammel's work either. Do you have a reference which I can access easily and make my own assessment of what he actually says, please?
If you deny the relevance of Energy in all this, then you are onto a loser if you want a valid theory. Leaves, at the top of a tree, were produced with materials, including water, that had to be carried up there from the ground. If that didn't require energy to raise the stuff in the first place then we have to seriously reconsider the whole of our understanding of everything. Energy is needed to lift the water for transpiration - where does it come from? (Using the accepted definition of energy please)

Your ideas could only be considered if you were to do a complete energy budget, in which you say how much energy is put in, where it comes from and how much is got out.
It needs more than just verbal arm waving. The shape and width of your tubes has no effect on the gravitational potential energy involved in lifting the water. You have, clearly not seen the ultimate relevance of my simplified rope model - the rope cannot evaporate - it is the water in the buckets that evaporates. The rope is the intermolecular attraction, if you like.
As I commented earlier. You just shift your ground rather than dealing with my specific objections. Is that true Science?

Evolving ideas about osmosis and capillary fluid
exchange1
H. T. HAMMEL
Department of Physiology and Biophysics, Medical Sciences Program, Indiana University School of
Medicine, Bloomington, Indiana 47405-4401, USA

www.fasebj.org/cgi/reprint/13/2/213

Energy is from the sun, evaporative energy from the atmosphere and gravitational force / energy from the planet. Simple enough?

Where is the energy that drives osmosis? Where is the energy that mystically sucks water from the ground to a hundred metres through the leaves in the Cohesion Tension Theory? Where is the energy that enables trees to soak up say 500 litres of water per day and allow it to flow out of the leaves? Where is the energy that mystically applies root pressure and squeezes water out of the leaves. Where is the energy that enables water to attract water to the canopy of a giant Californian Redwood?

Your ideas could only be considered if you were to do a complete energy budget, in which you say how much energy is put in, where it comes from and how much is got out.
It needs more than just verbal arm waving. The shape and width of your tubes has no effect on the gravitational potential energy involved in lifting the water. You have, clearly not seen the ultimate relevance of my simplified rope model - the rope cannot evaporate - it is the water in the buckets that evaporates. The rope is the intermolecular attraction, if you like.
As I commented earlier. You just shift your ground rather than dealing with my specific objections. Is that true Science?

It is your rope model that is in need of revision because it does not address experimental observations. The video on Youtube showing water flowing around a vertically suspended inverted u tube between to ground level vessels speaks volumes about the differences between your rope analogies.

For example picture your rope inside the 24 metre suspended tube, give it a tug on one side and watch it gather momentum as more and more weight is shifted to one side, the rope is pulled up on one side and falls down the other side.

Now picture two identical levels of water in 2 bottles with both open ends of the inverted 24 metre high tube placed at ground level inside the bottles, secured with wire. Initiate the flow by adding say 2 grams of salt to one side. Now we see a downward flow that is dragging on all of the water molecules pulling them in the direction of the falling solute and pushing the water molecules in front of the falling salt solution. But at ground level we see water displaced in one vessel and water level in the other bottle falling on the upward flowing side. Clearly there is an energy imbalance here because the level dropping does not reflect the amount of solute added.

I state exactly what was observed experimentally, you keep saying I change direction. I would defy anyone to replicate my experiments and produce a different result.

But the shape and width would clearly have an affect on your rope and bucket model and this is my point! You can’t have one rope on one side heavier than on the other side as it would cause it to rotate and fall to the ground.

The vessels inside a tree are not perfectly uniformed and do not balance upward with outward flow in either number or size yet it does not appear to affect the stability.

Rosy:
Andrew: I still haven't seen you do the maths with regard how energy is conserved in your proposed sytstem - I imagine you must have done it (it's a five minute calculation) - how much water (what mass of water) you would expect to draw to the top and leave there compared to the mass of the solution going down, if (as I think you believe) it is only gravity acting on the "down" arm that drives the raising of water to the top of the tree?
If you're planning to disprove the idea of the conservation of energy with your theory, it's as well to be explicit about it.

Lyner:
Rosy - I think your question has been addressed in something I have written during your post. The idea is that solar energy provides the energy for evaporation and a resulting difference in density produces some flow. The actual amounts involved are, as you say, not specified.
AKF
I am in the middle of reading that article - thanks, it is very interesting and, not surprisingly, is coherent, does not rely on hyperbole or words like "mystically" and has a lot of well related ideas.
I notice that he constantly refers to constraints imposed by energy and thermodynamic principles. He seems to account for every occurrence in a reasoned way. This is no surprise as he has academic discipline. I haven't yet seen where his ideas explicitly support what you are saying.

Returning to the ancient thread of the 'circulating' water tube. The water circulates when you add salt at a height because the hydrostatic pressure is increased and the flow just takes place because of an impressed force. You supplied energy for this movement by getting on some steps and carrying the salt solution up there. The energy turns up as gravitational potential energy in the difference in levels in your two bottom reservoirs. I can see no reason why the final difference in levels would be affected by where you put the salt. All that would count, in the end, would be the mass of salt you put into the tube and the resulting density change. You keep implying that it is the flow that makes things happen. It is, in fact, things that cause the flow. Once you stop adding salt, the flow will slow down and stop - when the pressures due to the total weights on each side balance the difference in hydrostatic pressure in the reservoirs. There is no suggestion, surely, that the process, once started, will carry on for ever. You could, in fact, achieve the same effect by introducing a stream of very small bubbles or a light oil into the up leg of the tubes. (Yes, I know that cavitation could be a problem but not in a short tube).
You say that the energy represented by the level difference does not correspond to the amount of salt added. You would need to justify that statement. To verify this you could use a U tube (not inverted), carefully add your solution to one side and measure the resulting height change (a long cotton wool plug would help avoid mixing of the water / solutions on each side. Otherwise, you could, of course, measure the density of your salt solution and do the conventional calculation. I have no idea of the amount of salt you used so I can't help you there.
Actually, your experiment does not show circulation- it shows transfer. If both ends were in the same reservoir, the circulation would only carry on whilst you were adding salt - the average concentration of the bulk would just keep increasing.

I am beginning to see what you may be getting at when you say what is going on at the top of the tree. You seem to be saying that the extraction of water at the top (as the solar energy causes evaporation) is increasing the density of the solution, which would provide a pressure imbalance and start a flow. The problem is that the difference in density is small and would require a large downward flow. Then, at the bottom, the plant would need to be disposing of this more dense liquid somewhere away from where it is picking up its fresh water. Without that, the inlet water would start to consist of more and more dissolved salts and the process would self limit. You would need to justify with actual figures (as always).

You may be able to model the system (for a short tube full of salt solution) by having a window near the top, on one side, with a semi permeable membrane - even some Gortex, which would let water evaporate and produce your concentration effect. The problem is that the construction of the membrane would have to be such that it let water molecules out but didn't let molecules of O and N in. The membranes in plants would have to be able to achieve this and may have to be smarter than you can get with non organic materials.

But, having accepted that something is going on, I can't see the relevance of the 'flow' idea of yours. The energy clearly comes from sunlight causing evaporation and by tension in the water column. What does the flow do for you - whilst it is essential for distributing food and oxygen around the plant, why do you want it to be part of the 'driving mechanism'?

BTW, are you still insisting that the circulation in our bodies is not actually driven by the heart? That's what you seemed to be saying in one of your other posts, some while ago.

Are you aware of the concept of Negative Potential Energy. That is what gravitational energy is. You can only 'get' energy from gravity by raising something above its rest position. That involves an energy input (positive). Gravity is no different from a spring, in that regard. Your first statement doesn't make sense, I'm afraid.

1. Irrigation in arid conditions leaves behind a crust of salt due to the high evaporation rates. This is what started my journey. Where trees were present in the arid areas, the crust of salt did not contaminate the land sufficiently to kill the trees given that these trees were well established and thriving.
2. The same saline contamination must also apply to vegetation, trees included, as they evaporate water effectively so one would expect a build up of salts at the leaf and we should see salted crowns on trees everywhere but normally we do not. Except for mangrove and a few others, but even these are not overly contaminated at the leaf.
3. Due to the effects of gravity on solutes, We should see salt and sugars accumulating at the roots and normally they do not except for a deciduous tree shedding it’s leaves, then we see a build up at the roots over the winter.
4. If the salts under normal active transpiration and circulation are not found at the roots, then there is a storage mechanism in the timber and no one can dispute that trees are very good at storing carbons and salts, in fact a paper I read a long time ago said trees were used to take up highly toxic heavy metals and lock them safely into the timber. But the dilute water arriving at the roots would suffice to re-dilute salts and sugars enabling the tree to actively transport them back to the leaf providing the upward flow is always more dilute than the downward flow and this appears to fit with the literature.
5. You mention the U tube experiment showing differences in levels. No cotton wool is required to keep the solutes from mixing with the solute free side. I have observed a suspended Youtube preventing diffusion for several weeks by using food colouring to monitor this. Will conduct the experiment again if you like and photograph it every day or you could try it and see for yourself. This presents more problems for the literature because diffusion is thought to be an influential driving force also.
6. Adding a gortex window is an interesting idea, however it would not work with the 24 meter experiment because the gortex would provide a cavitation seed point, unless the experiment was inside a water filled tube to support the water columns. “this reflects the trees structure more than the simplified Brixham experiment”
7. Gravity energy potential. Evaporation from the oceans provides rainfall that causes rivers to flow. No one has to lift anything anywhere it just happens every single day of the year. Evaporation from the ocean surface is all that is required to drive the Worlds ocean currents, an underwater river bigger and more powerful than all of the rivers in the world put together. So why are you trying to avoid the connection with density flow trees and plants?
8. Picture one salt laden molecule attached to all of the other water molecules in the tube experiment. How does it move away from the other molecules without affecting their motion? It can’t! If cavitation occurred the salty water molecule would apply a positive compressing force on all of the other water molecules “the butterfly effect in fluids”
9. The Heart inside a chickens egg does not beat at conception, How could it, the heart does not develop before the circulation is in place. Primary circulation is established long before the primary tubular structure of the heart develops. The egg need to be rotated and as it is egg shaped it can only be rotated across one axis under normal incubation, so why does the egg need to be rotated at all? Could the migration of salts through the albumen be initiating this primary circulation? If the heart was entirely responsible for circulation, which it clearly is not, then varicose veins should worsen when the head of the bed is raised by 15cm’s. After all, the medical establishment promote this idea by advising patients to sleep with the head of the bed lower, or raise the legs higher, yet it does not have any lasting effect on varicosity. So one would expect the medical establishment to re-think their logic and question their own misguided non-scientific belief system. Yet they continue to advise raising the legs knowing full well that it will be of no use long term and surgery will be required eventually. So there is something clearly wrong with the literature. Professor Hammel sent me a paper. Hammel said during a telephone conversation that he had observed a pulsate solute flow arriving at the kidneys and was very excited by the simplicity of the evaporative density flow.

Roles of colloidal molecules in Starling's hypothesis and in returning interstitial fluid to the vasa recta
H. T. Hammel
Department of Physiology and Biophysics, Indiana University, Bloomington 47405, USA.
To begin to understand the role of colloidal molecules, a simple question requires an answer: How do the solutes alter water in an aqueous solution? Hulett's answer deserves attention, namely, the water in the solution at temperature and external pressure applied to solution (T,pe1) is altered in the same way that pure water is altered by reducing the pressure applied to it by the osmotic pressure of the water at a free surface of the solution. It is nonsense to relate the lower chemical potential of water in a solution to a lower fugacity or to a lower activity of the water in the solution, since these terms have no physical meaning. It is also incorrect to attribute the lower chemical potential of the water to a lower concentration of water in the solution. Both claims are derived from the teachings of G. N. Lewis and are erroneous. Textbook accounts of the flux of fluid to and from capillaries in the kidney and other tissues are inadequate, if not in error, as they are based on these bogus claims. An understanding of the process by which colloidal proteins in plasma affect the flux of nearly protein-free fluid across the capillary endothelium must start with insights derived from the teachings of G. Hulett and H. Dixon. The main points are 1) colloidal molecules can exert a pressure against a membrane that reflects them and, thereby, displace a distensible membrane; 2) they can alter the internal tension of the fluid through which they diffuse when there is a concentration gradient of the molecules; and 3) only by these means can they influence the flux of plasma fluid across the capillary endothelium. However, the process is complex, since both the hydrostatic pressure and protein concentrations of fluids inside and outside the capillary vary with both position and time as plasma flows through the capillary.

Effect of a Salt Crust on Evaporation from a Bare Saline Soil
Haruyuki Fujimakia,*, Takahiro Shimanoa, Mitsuhiro Inoueb and Kazurou Nakanec
vzj.geoscienceworld.org/cgi/content/abstract/5/4/1246

Lyner:
A couple of comments- you have replied with overkill, as usual and I am overwhelmed.
Point 7. NoBODY carries the water up there into the clouds- the sun provides the energy for the latent heat of vaporisation. Isn't the water cycle taught in School?
Point 6. Of course a gortex window wouldn't work on a high tube. I said so. You wouldn't need to climb your cliff to test the idea. I doubt that the goretex would be impervious to air molecules for anything other than a few cms of head, unfortunately.
Point 9. Small animals do not need hearts because the chemical gradients are enough to get nutrients around by diffusion. Insects do not use a blood system for respiration either. You are so obviously convinced about the success of your treatment of varicose veins that you seem unable to consider that the explanation is anything other than your home-brewed one. Again, they are two separate issues. In mediaeval times, doctors often used to manage to make people well despite working on the Galen model for medicine.
Point 5. The difference in level will directly depend upon the difference in densities.How can it do anything else?

Points 1,2,3,4 Yes, of course salts move around in a plant but you are proposing that the salts have to move in order to make the flow happen. That is an entirely different matter.
Point 8. What is a "salt laden molecule"? afaik, salt exists as ions when in solution. What is laden with it?

Stefan
Andrew, your embryo argument has been refuted by several of us already. Please be less like a creationist and stop using it - how stupid do you think we are?

www.thenakedscientists.com/forum/index.p....msg216255#msg216255
www.thenakedscientists.com/forum/index.p....msg216702#msg216702
www.thenakedscientists.com/forum/index.p....msg216712#msg216712

More generally, it would be nice if you either become more sensible or stop arguing about physics and medicine altogether.