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Author Topic: How do Trees Really lift Water to their Leaves?  (Read 244727 times)

lyner

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Re: How do Trees Really lift Water to their Leaves?
« Reply #250 on: 10/11/2008 09:33:27 »
What has all that got to do with my fundamental question?

I would advise my students not to listen to someone who wouldn't answer a direct question.
« Last Edit: 10/11/2008 09:36:45 by sophiecentaur »
 

Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #251 on: 10/11/2008 17:14:08 »
Fascinating experiment showing a slice of water inside a solid wire frame.
Surface tension in water relies on cohesion in the water molecules. A droplet of water exhibits contraction of the surface water molecules due to cohesion pull. The following experiment in micro gravity shows graphically that:

1.   water does adhere to a metal wire. It also shows how water in micro gravity forms a globe. What does this suggest about the proposed copper tube experiment?
2.   The film of water shows the strength of cohesion and its stability is mentioned in hours rather than seconds. (that’s pretty strong)
3.   Not sure what the vanishing bubbles added to the water film tells us yet, but it certainly is interesting and could show graphically how cavitations are dealt with by trees.
4.   The paper towel used to draw water away from the captured water globule again shows that the adhesion to the wire does not affect the water’s ability to be drawn from the captive globule. So although adhesion is holding the water to the wire and the molecules of the water are under tension, the water can still be drawn away while the cohesive bond between the thin fim of water molecules resists the tendency to part even when other materials are added.
5.   The flow within the film of water shown by adding colouring is interesting, but unable to deduce whether there is some gravitational influence from the Earth, moon or even the mass of the station.
feature=related

Micro gravity is a good tool for allowing us to see how water exists inside the tube here on earth.
« Last Edit: 10/11/2008 17:20:31 by Andrew K Fletcher »
 

Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #252 on: 10/11/2008 17:42:16 »
feature=related

This video shows how strong the cohesive bond of a thin film of water really is subjecting it to boiling from a soldering iron and still it does not fail.
 

lyner

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Re: How do Trees Really lift Water to their Leaves?
« Reply #253 on: 10/11/2008 18:02:56 »
Never a straight response.
Are you surprised I wouldn't invite you to my School?
 

Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #254 on: 22/06/2009 09:19:09 »
How do trees really lift water to their leaves?
Author: Andrew K Fletcher

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? Or Capillary action. Can trees soak up water and release it into the atmosphere like a giant sponge, if this were 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 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, but a circulation driven by density changes caused by evaporation altering the sap within the leaves and branches not unlike our own circulation which also benefits from density changes in the fluids again caused by evaporation.
 

Offline witsend

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Re: How do Trees Really lift Water to their Leaves?
« Reply #255 on: 22/06/2009 11:10:25 »
I'm very happy with altrnate theories but why try and improve on osmosis?  Surely it explains everything?  I'm not sure that ANYTHING need be added to this process.  It's just that the roots can take up water and the leaves can give out water.  Perfect illustration of the same principle with reversed applications. 
 

lyner

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Re: How do Trees Really lift Water to their Leaves?
« Reply #256 on: 22/06/2009 11:25:26 »
Quote
The arguments for accepted explanations for fluid transport in trees has not been forthcoming, in fact this thread has shown they are indeed flawed.
AKF. Why are you resurrecting this?

So your argument is not flawed?
As a matter of fact, you have no scientific argument at all. You keep repeating purple passages and the quoting the same instances. Is there any new development in research since you last posted?
We established that, in your smooth tube, you could get a measurable effect from cohesion in water which was a surprise to me. I have accepted that it happened. But is does not explain where the energy comes from.

 Your explanation ignores the rest of Science on the grounds that you are ignored due to lack of qualifications.  The reason that I / we don't accept your explanation for the phenomenon is because it is not a scientific one. You are  hanging it all on the idea of cohesion vs adhesion. However, the Science which applies everywhere else in the World is not allowed to act inside plants - according to you. Isn't Science supposed to be consistent?

Whilst we are 'imagining', lets discuss your circulatory model and use a simple mechanical model.
Take a long loop of rope hanging over a pulley at the top of a building. Tie buckets at regular intervals onto the rope.  Fill each bucket with water and add some stones. The stones represent your dissolved salts.
The buckets are spaced equally on the rope, for a start. (This is a simple model, so you have to ignore the problem of getting the buckets over the pulley at the top if the rope moves around - but that could be solved, of course.)

As an analogy to your transport theory, some water and some of the rock leaves the topmost bucket - leaving it half full and with most of the rock in it. It is now lighter than all the other buckets. Manually pull one side of the rope down and half empty the next bucket and the next and the next, as they reach the top and go over. There is now an imbalance. One side of the rope has less load than the other which, left to itself, will pull the emptier buckets back up to the top and those full of water will fall back down. You won't get a circulation.
The only way that you can sustain the motion is for someone at the top to be putting more rocks into the buckets that you want to go down. To lift water constantly, you need fractionally more weight to be added on the other side - constantly.
In a plant, the only source of extra weight, up there with the leaves,  is C from the CO2  from the air (during photosynthesis).  Just do the sums - compare the mass of water lost during transpiration with the mass of food produced by photosynthesis. There are just not enough 'extra rocks' produced at the top to pull the required amount of water up in the buckets. As I have so often said -The Numbers Count!
I have avoided using the Energy word because you have ignored its use in the past. The above, very mechanical, model shows that your proposed system cannot work. Can you possibly have an argument against what I have written?
 

Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #257 on: 22/06/2009 20:19:39 »
Quote
Your explanation ignores the rest of Science on the grounds that you are ignored due to lack of qualifications.  The reason that I / we don't accept your explanation for the phenomenon is because it is not a scientific one. You are  hanging it all on the idea of cohesion vs adhesion. However, the Science which applies everywhere else in the World is not allowed to act inside plants - according to you. Isn't Science supposed to be consistent?

Not hanging it on the idea of cohesion versus adhesion, this argument was for the tubular experiments, which of course applies to the density flow theory also. Science is supposed to be consistent but it clearly is not when there are errors in the science!


Quote
Whilst we are 'imagining', lets discuss your circulatory model and use a simple mechanical model.
Take a long loop of rope hanging over a pulley at the top of a building. Tie buckets at regular intervals onto the rope.  Fill each bucket with water and add some stones. The stones represent your dissolved salts.
The buckets are spaced equally on the rope, for a start. (This is a simple model, so you have to ignore the problem of getting the buckets over the pulley at the top if the rope moves around - but that could be solved, of course.)

You appear to be missing a huge chunk of information in your analogy. Let me try to clear it up for you.

Picture a 3 mil bore tube (for instance) as one ascending limb, in this case representing the phloem, which is predominantly downward flowing sap and has far more dissolved solutes in it than the predominantly ascending sap in the xylem vessels. (published science).

Now back to the tubular experiment which admittedly is a simplified model designed only to show the density flow and that cohesion and adhesion play a part in the experiment, although I suspect not an equal part, but let’s ignore this for now.

In our ascending tube we use say 6.5mm bore tubing and do not include any salt for the moment. We raise our unequal bore tube up to say 24 meters and we do not see a flow in either direction but a stagnation of water suspended inside both the 3 mil bore tube and the 6.5 mil bore tube. In fact we could probably show 2 tubes attached to one side and a single tube attached to the other side providing there is a smooth uninterrupted bore at the upper most part of the suspended tube. All ends are open to the atmosphere but suspended in a bottle or bottles filled with water and at equal levels with the ground.

Now, let us see how this fits with your rope and bucket analogy. Ok let’s ignore the buckets and rocks for now. If we had a rope that was the same diameter and the same molecular weight, the rope with careful positioning could indeed stay suspended as there would be an equal counterbalance.

But let’s add a rope twice the size and twice the weight on one side of the pulley. Of course we would see one side pulled down by gravity and the lighter rope side drawn up without any added weights.

In the experiment and inside the tree or plant, there is an equalizing fluid balance that takes away the need for raising the fluids or indeed suspending the fluids.

Unlike the simplified experiment the tree has a multi conduited system inside a larger conduit, the bark with its roots beneath the soil. This is important in this instance because like the bottles of water, it offers support for the columns due to the air soil and water pressure applied to the outside of the tree and more so to the roots.

Yet if we cut the roots off or indeed run a chainsaw through the multiconduited tree system we do not see water oozing out but the water inside retracts up the severed trunk, and this also happens when the ends of the tubes are pulled from the bottles while the water is suspended inside the inverted U tube.

Now back to the flow and return system. According to the above explanation and indeed observations, we can have several upward flowing xylem vessels that are counterbalanced by a ingle downward flowing phloem vessel (for arguments sake) This would give us a mechanism for shedding a huge volume of water at the leaves while returning a smaller yet denser volume down the phloem vessel. Again this experiment was conducted albeit a scaled down version of the Brixham Experiment. “ x ascending salt free and one descending tube attached at the centre which was raised to 2.5 metres. Result was that the flow and return continued to work regardless of the weight on either side of the inverted U tube.

The extra molecular weight at the leaf is not entirely relying on CO2. For example, a deciduous tree that has shed it’s leaves cannot rely on CO2 but somehow manages to circulate fluids to the emerging buds.

You have overlooked the nutrients and colloids from the soil, these are delivered to the leaves in dilute solution and MUST be concentrated by evaporation!  Sugars are produced at the leaf from CO2 but cannot be produced if there are no leaves!

Inside the deciduous tree that has shed it’s leaves we have suspended sugars and salts, most of which migrate to the roots during the fall again verifying the need for gravity in any theory that addresses the ascent of sap in tall trees. All that would be required for circulation to continue is an unequal density in the sap and the warmth during the spring and summer provides an external heat / density change to the sap, sufficient to trigger an increase in circulation, but also an increase in positive pressure at the branches, providing the impetus for buds to emerge.

Yes I do have an argument, not against your work an motion analogy but against how you have applied it to a fluid based system.

Andrew

P.S. Yes there has been a huge development recently with regards to publication. 
« Last Edit: 22/06/2009 20:49:03 by Andrew K Fletcher »
 

lyner

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Re: How do Trees Really lift Water to their Leaves?
« Reply #258 on: 22/06/2009 23:09:20 »
So a few lines of total logic are answered with far too much verbiage to even read, let alone answer.
You have not answered the overwhelming fact that, somewhere, you have to produce an equal WEIGHT of falling water plus stuff  (plus a little bit) to balance the amount of water you need to raise.  (You would not argue against the idea of vast amounts of water being transpired, I presume) Whether you are discussing 20m or 1cm. Where do all these extra weights - ropes, salts etc. come from way up there in the tree? If you want to pull something up you need something to pull it down with. If you want the process to continue, according to your model, you keep needing extra weight added at the top.  Where could it possibly come from? This is not Science - it's what a child with a construction kit would conclude. It could not work on that principle.
Can  you really not understand that?

I wonder why I bother, sometimes.
« Last Edit: 22/06/2009 23:46:45 by sophiecentaur »
 

Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #259 on: 23/06/2009 00:06:33 »
Try the Bleep experiments before you jump to conclusions!

Listen to what has been said!
 

Offline witsend

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Re: How do Trees Really lift Water to their Leaves?
« Reply #260 on: 23/06/2009 05:50:47 »
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?  Altenate 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. 
 

lyner

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Re: How do Trees Really lift Water to their Leaves?
« Reply #261 on: 23/06/2009 07:49:25 »
We frequently find that alternate Science theories just change direction to suit rather than dealing with inconsistencies. If a molecule interacts chemically or mechanically with its neighbours in a particuar way under one set of circumstances then, unless conditions are radically changed, we normally expect it to behave the same way in another set.
Just how the molecules are supposed to know they're in a tree and not in a tube beats me. Unless it's supposed to be the 'flow' that sustains the flow - being perpetual motion.
 

Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #262 on: 23/06/2009 12:05:46 »
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?


We frequently find that alternate Science theories just change direction to suit rather than dealing with inconsistencies. If a molecule interacts chemically or mechanically with its neighbours in a particuar way under one set of circumstances then, unless conditions are radically changed, we normally expect it to behave the same way in another set.
Just how the molecules are supposed to know they're in a tree and not in a tube beats me. Unless it's supposed to be the 'flow' that sustains the flow - being perpetual motion.
 

Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #263 on: 23/06/2009 13:18:23 »
Witsend. 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? 
 

Offline witsend

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Re: How do Trees Really lift Water to their Leaves?
« Reply #264 on: 23/06/2009 17:25:08 »
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.
« Last Edit: 23/06/2009 17:27:10 by witsend »
 

Offline witsend

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Re: How do Trees Really lift Water to their Leaves?
« Reply #265 on: 23/06/2009 18:05:52 »
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

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Re: How do Trees Really lift Water to their Leaves?
« Reply #266 on: 24/06/2009 21:53:27 »
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?

Spelling edit
« Last Edit: 25/06/2009 09:59:41 by sophiecentaur »
 

Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #267 on: 25/06/2009 11:42:13 »
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

http://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?

Quote
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.



 

Offline rosy

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Re: How do Trees Really lift Water to their Leaves?
« Reply #268 on: 25/06/2009 13:40:05 »
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

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Re: How do Trees Really lift Water to their Leaves?
« Reply #269 on: 25/06/2009 14:03:36 »
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.

 

Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #270 on: 25/06/2009 18:08:38 »

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
http://vzj.geoscienceworld.org/cgi/content/abstract/5/4/1246

 

lyner

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Re: How do Trees Really lift Water to their Leaves?
« Reply #271 on: 25/06/2009 19:19:10 »
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?
 

Offline _Stefan_

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Re: How do Trees Really lift Water to their Leaves?
« Reply #272 on: 25/06/2009 21:00:45 »
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?

http://www.thenakedscientists.com/forum/index.php?topic=18961.msg216255#msg216255
http://www.thenakedscientists.com/forum/index.php?topic=18961.msg216702#msg216702
http://www.thenakedscientists.com/forum/index.php?topic=18961.msg216712#msg216712

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

Offline witsend

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Re: How do Trees Really lift Water to their Leaves?
« Reply #273 on: 25/06/2009 23:33:23 »
Andrew, the point here is that Sophiecentaur does to original thought is what rain does to fire and dampness does to squids.  I'm beginning to get an obsessive interest in the personality type.  But I would strongly recommend that you don't try and reason with him unless you actually quote from a text book.  He has a certain stiffness.  A want of flexibility.  Struggles a little with the abstract thought.  And he trawls through the new ideas threads because he's determined to kill any such, at birth.

He's also a scientist who makes up his mind about an experimental results without doing the experiment.  Rather a contradiction in terms. So don't get discouraged.  Then he'd have achieved his object.  He's not interested in the idea.  He's only determined to put you down.   



 
 

lyner

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Re: How do Trees Really lift Water to their Leaves?
« Reply #274 on: 25/06/2009 23:38:41 »
witsend
I guess you would say the same about anyone who had their feet on the ground.
I have built your circuit many times. It's a relay driver. They work conventionally.

I should listen to your friends. If they wonder why you posted your idea on a forum then perhaps so should you.
 

The Naked Scientists Forum

Re: How do Trees Really lift Water to their Leaves?
« Reply #274 on: 25/06/2009 23:38:41 »

 

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