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Author Topic: How do Trees Really lift Water to their Leaves?  (Read 244776 times)

Offline rosy

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Re: How do Trees Really lift Water to their Leaves?
« Reply #25 on: 27/04/2005 17:37:58 »
Hm, yes... I agree not exactly a siphon in the traditional sense... but i can't see why that matters. Whatever the source of the upward "pull" on the water at the top of the left hand column, it's still just a pull at that point, as would be the pull due to transfer of the water across a cell membrane by osmosis.
I really can't see where this tells us anything new.

BTW I think the guys are talking about this
http://www.the-tree.org.uk/TreeTalk/3Spring2003/Gravity/gravity1.htm
webpage, I googled it but I thought I'd link it to save others the bother (as I couldn't find it higher up the thread).
 

Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #26 on: 27/04/2005 18:32:32 »
Rosy
Thanks for agreeing with me on the non-siphon effect.
Strange that you cant find anything new in this? The flow rates observed within this simple paradigm parallel any observed rates in trees or plants, if not exceed them with ease. That being because of the obvious fluid friction within a tree or plant and the lesser degree of friction in the tubular models.

One should not jump to the conclusion that current understanding of osmosis is comparative to the efficacy of the new paradigm, without first testing the simple tubular experiments for oneself.
 
Andrew


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Offline daveshorts

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Re: How do Trees Really lift Water to their Leaves?
« Reply #27 on: 27/04/2005 19:09:11 »
You had at in the experiment a loop of tube filled with water with a height difference from the top to the bottom of more than 10m? So you have prooved that a column of water more than 10m high is stable, so why shouldn't a xylem be able to do the same thing? Especially as it has had 200million years to optmise this process.

You are right what you were doing (injecting denser fluid near the top of the tube on one arm of a syphon loop) is not conventional syphoning, you are making one arm of the syphon heavier by using a higher density fluid rather than by using a lengthened arm, but if this works then a syphon will work.

If the water column has not cavitated there is no reason why it shouldn't syphon - the reason why it is often said that you can't syphon over 34 feet is that the fluid will have a tendancy to cavitate. How far did you lower your bottle, and for how long? If your tube was 150feet long a the system will have a resonant period of about 45 seconds (assuming that there is no damping, which would make this period longer), so to definitely see any effect you would have had to wait at least this long.

What you describe in your 'tubular experiments' sounds entirely reasonable to me and exactly what I would expect to happen from standard physics, but I don't see how it would apply to a tree.

Although you get a downward flow of sugars through the Phloem and an upward flow through the Xylem, as you mentioned earlier, 98% of the water that is lifted up is evapourated, so the less than 2% of water going down would have to lift 20 times that amount of water.
 For the syphon device you describe in the link to work the weight on the downward side must be greater than the upward side or it obviously won't work. Unless the density of the sugar solution is 50 times that of the water coming up I don't see how this could work.


btw. You came to a hands on science event I was running in Brixham a couple of years ago.
 

Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #28 on: 27/04/2005 21:15:37 »
You had at in the experiment a loop of tube filled with water with a height difference from the top to the bottom of more than 10m? So you have prooved that a column of water more than 10m high is stable, so why shouldn't a xylem be able to do the same thing? Especially as it has had 200million years to optmise this process.

*****Answer
A little more than 10 metres actually, 24 metres to be exact, as that was the length of tube I was using at the time.

The column of water is not stable in the tubes, cavitations is demonstrated as the stress on the water bead causes bubbles to form and the columns collapse eventually, just as they do in the tree.
*****



You are right what you were doing (injecting denser fluid near the top of the tube on one arm of a syphon loop) is not conventional syphoning, you are making one arm of the syphon heavier by using a higher density fluid rather than by using a lengthened arm, but if this works then a syphon will work.

*****Answer
Feel free to try your siphon at these heights. Ill bet you draw the same conclusion that many others have already observed as the accepted height at which a siphon will work.

Picture a loop of tubing suspended above the 10 metre limit, producing an unbroken bead of water, under the tension produced by the equal weight of the water on both sides of the tubes. Now initiate the lowering of one of the ground based bottles to try to cause a siphon. The result would be that the lowering of the one bottle would merely cause the bead of water to become elasticised and stretch to the point where it would collapse. But during the stretching process, we hypothetically inject a tiny amount of concentrated saline solution coloured, in one side of the loop at the top/upper most part of the loop. The result would be an obvious independent flow and return system, within the pre tensioned bead of water, flowing with total disregard to pressures, and creating its own pressure changes within the tension placed upon the bead of water.
This flow system does not require pressure in order to function, but delivers pressures as it functions.
*****


If the water column has not cavitated there is no reason why it shouldn't syphon - the reason why it is often said that you can't syphon over 34 feet is that the fluid will have a tendancy to cavitate. How far did you lower your bottle, and for how long? If your tube was 150feet long a the system will have a resonant period of about 45 seconds (assuming that there is no damping, which would make this period longer), so to definitely see any effect you would have had to wait at least this long.

*****Answer
Wrong, there is a fundamental reason why siphon does not occur as explained above.

The bottle was lowered 2 steps, presumably around half a metre, as I did not measure the steps, and remained for well over your 45 seconds without any evidence of siphon.

What you describe in your 'tubular experiments' sounds entirely reasonable to me and exactly what I would expect to happen from standard physics, but I don't see how it would apply to a tree.
*****Answer
According to the points you raise above, this is not quite correct, as your understanding of the siphon does not apply here.
*****

Although you get a downward flow of sugars through the Phloem and an upward flow through the Xylem, as you mentioned earlier, 98% of the water that is lifted up is evapourated, so the less than 2% of water going down would have to lift 20 times that amount of water.

*****Answer
This paradigm can lift many thousands of times the volume going up, and only requires a minute of solutes flowing down to cause the greater volume of less dense solution to flow up, giving the tree more than enough water to evaporate and produce a denser sap.
*****
For the syphon device you describe in the link to work the weight on the downward side must be greater than the upward side or it obviously won't work. Unless the density of the sugar solution is 50 times that of the water coming up I don't see how this could work.
*****Answer
This is where you go wrong David: imagine a 24 mil bore tube on one side and a 6 mil bore tube on the other side, blended seamlessly together to form a single looped open ended tube of different sizes immersed at equal levels in two bottles of water, suspended 24 metres vertically by the centre. The weight of the 24 mil bore side of the loop will be counterbalanced exactly by the 6 mil bore side of the tube, with no net movement either way. Now add the tiny amount of salt to the 6 mil bore side at the centre and circulation begins. In the case of the tree, the structure and size differences of the tubes compensates for the loss of moisture through the leaves and returns the resulting concentrates back towards the ground.


btw. You came to a hands on science event I was running in Brixham a couple of years ago.


I do remember popping in the town hall now you mention it, as you were closing your event I believe.

Thank you for remembering me.

Andrew
 


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Offline daveshorts

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Re: How do Trees Really lift Water to their Leaves?
« Reply #29 on: 27/04/2005 22:56:47 »
quote:
imagine a 24 mil bore tube on one side and a 6 mil bore tube on the other side, blended seamlessly together to form a single looped open ended tube of different sizes immersed at equal levels in two bottles of water, suspended 24 metres vertically by the centre. The weight of the 24 mil bore side of the loop will be counterbalanced exactly by the 6 mil bore side of the tube, with no net movement either way. Now add the tiny amount of salt to the 6 mil bore side at the centre and circulation begins.


This system will produce a flow, but because the amount of water in the system is allways the same, if you get 1 litre falling out of the 6mil tube, the 24mil tube will suck up 1 litre, however because the area of the bigger tube is 16 times larger the water you have sucked up will only go up 1/16th of the tube, you haven't pumped any water to the top.

quote:
In the case of the tree, the structure and size differences of the tubes compensates for the loss of moisture through the leaves and returns the resulting concentrates back towards the ground.


But how are you getting the water out at the top? The water is at a negative pressure, this means that to get it out you have to pull, and pull very hard against a large pressure. Evaporation will do this, but if evapouration is doing the  work you don't need the tube coming down and that is just the conventional model you are so dead set against.


In what way has your system produced a net flow of  water to the top of the cliff? Overall you have moved water from one jar to another one next to it. If you had filled a bowl of water at the top of the cliff that would be equivalent to what the tree is doing, and I will belive it could be an issue when you can do that.
 

Offline daveshorts

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Re: How do Trees Really lift Water to their Leaves?
« Reply #30 on: 27/04/2005 23:00:14 »
quote:
Picture a loop of tubing suspended above the 10 metre limit, producing an unbroken bead of water, under the tension produced by the equal weight of the water on both sides of the tubes. Now initiate the lowering of one of the ground based bottles to try to cause a siphon. The result would be that the lowering of the one bottle would merely cause the bead of water to become elasticised and stretch to the point where it would collapse. But during the stretching process, we hypothetically inject a tiny amount of concentrated saline solution coloured, in one side of the loop at the top/upper most part of the loop. The result would be an obvious independent flow and return system, within the pre tensioned bead of water, flowing with total disregard to pressures, and creating its own pressure changes within the tension placed upon the bead of water.

So would it break if you lift one of the jars, which will reduce the tension in the water column...?
 

Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #31 on: 27/04/2005 23:35:45 »
Yes David, cavitation will inevitably cause the columns to collapse. The additional tension placed upon the bead by lowering the level of one side, merely serves to hasten the process of cavitation. Even if you raise a jar following initial lowering, the cavitation is already underway. In the link that Rosy put on her post, I have tried to address the way cavitations continually form and self repair within the multi conduit system of a tree. Cavitations do not interfere/interrupt the flow within the narrow tubes of the bench top model. In fact, the cavitations/bubbles behave oddly when sufficient saline solution is added. They are observed to flow down instead of up, and there is water flowing around the bubbles also.

Fascinating to see bubbles flowing down instead of up. Maybe you might want to test the simple bench top version for yourself?




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Offline daveshorts

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Re: How do Trees Really lift Water to their Leaves?
« Reply #32 on: 27/04/2005 23:47:51 »
But there is no difference in the pressure of the water at the top of the tube, between your clifftop experiment  and an equivalent syphon, so I don't see why you think one will work and the other won't. What sized tube did you use for your experiments?
 

Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #33 on: 28/04/2005 08:43:11 »
Yes! Altering the heights of the 2 jars merely serves to place additional stress on the fluids within the unbroken bead of water. Therefore, the collumn is not permanently stable, as is so in the tree and plant. The tree gets around this problem by having an outer sleeve (bark) and a multi conduit system inside the outer sleeve. This enables the resulting pressure change when cavitation occurs, to gain height due to the resulting downward force on the broken bead, pushing up fluid under greater force to refil the broken bead.


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Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #34 on: 28/04/2005 08:56:22 »
quote:
Originally posted by daveshorts

quote:
quote]

This system will produce a flow, but because the amount of water in the system is allways the same, if you get 1 litre falling out of the 6mil tube, the 24mil tube will suck up 1 litre, however because the area of the bigger tube is 16 times larger the water you have sucked up will only go up 1/16th of the tube, you haven't pumped any water to the top.


The model is simple, I do not have the time nor the inclination to try to construct a perfect artificial tree.

I only have to show the driving force in this paper. The trees design takes care of evaporation as the water and minerals flow though its veins

quote:
In the case of the tree, the structure and size differences of the tubes compensates for the loss of moisture through the leaves and returns the resulting concentrates back towards the ground.


But how are you getting the water out at the top? The water is at a negative pressure, this means that to get it out you have to pull, and pull very hard against a large pressure. Evaporation will do this, but if evapouration is doing the  work you don't need the tube coming down and that is just the conventional model you are so dead set against.

Common sense should tell anyone that there is no attempt to extract water from the tubular models


In what way has your system produced a net flow of  water to the top of the cliff? Overall you have moved water from one jar to another one next to it. If you had filled a bowl of water at the top of the cliff that would be equivalent to what the tree is doing, and I will belive it could be an issue when you can do that.



I have never seen a bowl of water at the top of any tree other than those left by the owners of apple trees to prevent scrumpers.

In the case of a tree, we could place a plastic bag over a branch and collect and extract the condensed water in its canopy.

It is possible to design a model that can lift sea water, extract pure water and return the denser ballast to the sea through a tube in order to provide the pumping for the desalination. But I have long since given up jumping though loops to amuse people.





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Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #35 on: 28/04/2005 09:05:10 »
Quote
but if evaporation is doing the work you don't need the tube coming down and that is just the conventional model you are so dead set against. [quote/]

Evaporation is doing the work. But not in the way it has been erroneously interpreted by Dave et al. I am perplexed that you have stated that there is no downward flow in trees?

From an earlier post in case you missed it:
Transport of salts

The liquid which travels in the xylem is not, in fact pure water. It is a very dilute solution, containing from 0.1to1.0% dissolved solids, mostly amino acids, other organic acids and mineral salts. The organic acids are made in the roots; the mineral salts come from the soil. The faster the flow in the transpiration stream, the more dilute is the xylem sap. Experimental evidence suggests that salts are carried from the soil to the leaves mainly in the xylem vessels.

The xylem sap is always a very dilute solution, but the Phloem sap may contain up to 25 per cent of dissolved solids, The bulk of which consists of sucrose and amino acids.

There is a good deal of evidence to support the view that sucrose amino acids and may other substances are transported in the phloem. The movement of water and salts in the xylem is always upwards, from the soil to the leaf. But in the phloem the sap may be travelling up or down the stem. The carbohydrates made in the leaf during photosynthesis are converted to sucrose and carried out of the leaf to the stem. From here the sucrose may pass upwards to growing buds and fruits or downwards to the roots and storage organs. All parts of a plant which cannot photosynthesise will need a supply of nutrients bought by the phloem. It is possible for substances to be travelling upwards and downwards at the same time in the phloem.


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Offline rosy

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Re: How do Trees Really lift Water to their Leaves?
« Reply #36 on: 28/04/2005 10:24:59 »
Hm, I'm not at all convinced.
Transport of sugars between living cells (such as in the phloem) actually requires the input of energy. Sugars use ATP (the cellular energy transfer compund) to move sugar (and amin acid, and any charged or bulky species) molecules across cell membranes, including across the boundaries between seive plates.
I simply can't see how this is compatible with the idea that the gravitational potential of the more concentrated solution is lifting the water up the xylem.

quote:
It is possible to design a model that can lift sea water, extract pure water and return the denser ballast to the sea through a tube in order to provide the pumping for the desalination. But I have long since given up jumping though loops to amuse people.
 


I can't imagine how... no need to design a system, but would you like to outline the general principles...?
 

Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #37 on: 28/04/2005 12:55:43 »
Rosy, please repeat the simple experiments and understand the driving forces of nature.

If you cant get hold of the tubes, joints and syringe body, let me post them to you.

1. It is an impossibility of the highest degree for evaporation to take place from a liquid containing solutes of salt and sugars, without concentrating said solutes.

2. It is a function of gravity to act upon said solutes when they occur at an elevated point above less concentrated solutes. (see Atlantic conveyor system)

3. For every action there is a reaction. Any downward flow will cause an inevitable upward flow!

4. The experiments have been demonstrated at Primary level education, in schools. At secondary schools, at Universities, at Derriford Hospitalís Physics Department in Plymouth. At the London International Inventions Fair in 1997, witnessed by some 3 thousand visitors and inventors. On Westcountry Television News, BBC Radio in Paignton, and has not yet failed to convince all who have witnessed its efficacy in delivering the flow rates observed in plants and trees!

Now why canít you understand the simplicity of this discovery and its many applications?

Nevertheless, I am grateful for all of the replies on this thread and thank you for your input

Andrew


 

Offline rosy

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Re: How do Trees Really lift Water to their Leaves?
« Reply #38 on: 28/04/2005 13:35:26 »
I know how the experiment works. That's not my question.
It's quite obvious from your description how the weight of the solution pulls the (lighter) water over the top of the tubing.
But at the top of the loop, as in a conventional siphon, the water is at much less than atmospheric pressure (it has to be as there's a force holding up the column of water below) so I don't see how you propose that the water gets out of the xylae into the leaves (essentially the question Dave put further up the thread).

You haven't explained to me how your proposed system for lifting sea-water works.
 

Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #39 on: 28/04/2005 13:40:16 »
The following review came from a letter I wrote to professor H T Hammel,
who is member of the Max Plank Institute.



Within a 2 weeks I received his reply

INDIANA UNIVERSITY

SCHOOL OF MEDIICINE date September 6/ 1995

Dear Mr Fletcher:

I received the information you sent me regarding your ideas about fluid
transport in trees, in tubing and in the vascular system in humans.

I will study your ideas and comment upon them as soon as possible. A Quick
scan of your Brixham experiment prompts me to ask if you conducted this
experiment with boiled water without any solute added to the tubing on
either side of the central point which you raise 24 meters? I expect that
you could raise the tubing to the same height with or without solute in the
water. In any case , your experiment confirms that clean water (water that
is unbroken water, water that is without a single minute bubble of vapour)
can support tension of several hundreds of atmospheres. The record tension
obtained experimentally is 270 atmospheres. At 10 degrees C. (c.f. Briggs,
L. Limiting negative pressure of water. Journal of Applied Physics 21:
721-722 1950).

I expect even this tension at brake point can be exceeded by careful
cleansing of the water, to remove even the most minute region of gas phase.
When the water is already broken, as occurs when gas is entrapped on
particulate matter in ordinary water, the water will expand around even a
single break when tension (negative Pressure) is applied to the water. When
you boil the water, prior to applying (2.4-1) ATM negative pressure to the
water in the highest point of the tubing, you eliminate some of these breaks
in ordinary water. I expect that dissolving NaCl or other solutes in the
water will have little or no effect on the way you measure the tensile
strength of water.

I am enclosing some reprints that may interest you. Some of these deal with
negative pressures we have measured in tall trees, mangroves and desert
shrubs. Other reprints deal with how solutes alter water in aqueous
solutions and how colloidal solutes (proteins) affect the flux of protein
free fluid between plasma in capillaries and interstitial fluid.

Sincerely H.T. Hammel Ph.D.


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Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #40 on: 28/04/2005 13:42:16 »
From: Hemetis
To: AndrewKenneth Fletcher
Sent: Saturday, March 04, 2000 2:51 AM
Subject: RE: NEW THEORY FOR FLUID TRANSPORT Re: How does water really reach
the tops of trees?08/August/1999


Hi Andrew :-)

You have the honor of being a true scientist and experimentalist.
Yet you have to answer for some big questions.
1- You have to explain the results of "Strasburger 1893" who killed the
lower part of an Oak with picric acid and demonstrated that "all" the stem
raised a "Fuchsin aquatic solution".

****
I am not familiar with the above mentioned experiment and would appreciate
more details.

Acid rain causes the death of many trees. Has anyone considered the fact
that an increase in acid will cause an increase in the rate at which
minerals are dissolved. For instance, if I pour battery  acid on concrete,
it dissolves!

If you increase the amount of minerals in water, you increase the specific
gravity of said water. When you relate this to the Brixham Exp. Any increase
in the S.G. of the water contained in the upward flowing side of the tube
will reduce the flow in the downside!

If the water at the said container becomes too heavy, the experiment would
stop or at least slow down to the point of almost stopping. The tree would
face the same problems according to the gravity theory. However, if the
weather conditions promoted accelerated evaporation from the leaves, this
would compensate for the heavier water at the root and transport would
continue.

Killing the bottom part of the tree would not cause the circulation to stop,
it would not even prevent the tree from drawing water from the soil.
The xylem is after all already dead and the downward flow would simply find
another route, possibly into a xylem, or by oozing from a damaged part of
the tree.




2- There is an established "Cohesion theory" which explains most of your
theory and you have to show what is the difference.

****
I am unaware of anyone showing water flowing vertically up to 78 feet.

Correct me if I am wrong, but cohesion simply explains how water bonds to
water. I fail to see how this could explain bulk flow vertically up or down.

As for chemical reactions at the leaf causing electrical influences on water
and then effectively transporting a hundred gallons of water from the roots
of a mature oak to the leaves, just does not work for me. If it has been
shown experimentally, I will swim the ocean and shake your hand tomorrow.

Once you have observed water flowing in tubes, and I sincerely hope you will
try at least the benchtop model, you cannot deny the existence of gravity
driven circulation! The efficiency of this system sets it aside from all
other attempts to explain fluid transport.

Since 1994, I have convinced many scientists, including Professor Edzard
Ernst at Exeter together with three doctors, Professor Michel Cabanac,
University Laval, Quebec. Professor H.T.Hammel. Emeritus member of the Max
Planck Instiute, Dr David Cutler, Kew Gardens, Forestry Commission
Scientists- who also attended the Brixham Exp. Professor Chui Exeter
University. and many many more. Yet nothing happens. I also know the reasons
why nothing happens!

3- If "salt solution" must "fall under gravitation to pull a water column up
and that is how the plant "feeds", how can you explain water circulation in
horizontal plants being so ordered as xylem feeding forward and phloem
feeding backward?

Horizontal flow? If I lay a water filled tube horizontally, with salt
solution added at the middle of the tube and the ends capped off, there
would be water transport spreading outwards from both sides of the saline
solution, and in order for this to happen, clean water would be drawn
towards the centre of the salt solution.

Even horizontal plants are elevated to some degree above ground level and
roots are usually below the surface of the soil. this is all that is
required to trigger transport.

4- How do you explain the homogeneity of climbing plants when they make a
down turn following the light- intensity?

The energy source in the soft part of plants would alter the pressures in
the xylem and phloem on one side of the stem, causing the plant to turn
towards the energy source.

Imagine a length of string attached to the trunk and running through soft
new growth in a tree. Give the string a pull and the branch is bent towards
which ever side the string is inserted.


5- In some ground plants the stem grows horizontally on the ground and we
can see multiple root systems along the stem and multiple shoot systems as
well, How do you explain the sap streams in such a plant, where all roots
absorb water and all shoots transpire. What is the direction of the flow?
where does your theory fit?
Do you think it is bidirectional? Or do you have to admit that the dead duct
network provides the path to the living parts, where one would push and
another would pull "on demand" and on cell to cell interactions.

The new shoots and roots would set up an independent flow system, which uses
the main flow systems water to operate. Take a cutting and it grows
independently to the plant it is cut from.

The roots on such a plant face down and the leaves point up.


So, yes your experiment is a wonderful verification for the Cohesion theory
which explains the minimum requirement of energy for water transport in a
living plant, where mineral and sugar diffusion from production line to
assembly of polymers locations would pull the associated water along with it
and must be replaced "Cohesively".

6- In many houses we have hanging pots for plant decoration in which plants
"hang down from the pot.
Do you have the slightest doubt that water in xylem is moving down and water
in phloem is moving up?
This should disprove your theory completely.

You can't disprove the truth! You can cloud its validity with words, but
clouds have a nasty habit of letting the light through at times.

Oh boy, do I have some doubts.

If  I shaped my tube loop to the exact shape of the plant you refer to and
released the saline solution at the same point as the leaves would release
their sap, you would still see gravity driven circulation, from a single
cell to a giant redwood, it makes no difference to gravity. Try it!
Furthermore, if there is a U bend in the plant, roots will form at the
bottom of the loop and this is used effectively to take cuttings from some
plants by pegging a branch so that it is covered in soil.


So think deeply because your contribution to science is valid experimentally
but your theory is defective.
That is why I have been repeatedly encouraging you to study plant physiology
deeply and check the established theories profoundly before you postulate a
new one.

We are studying plant physiology deeply as we exchange views and I am very
grateful for the opportunity to share your knowledge.

I do have a fair bit of knowledge in this field. However my work has led me
to helping people with neurological conditions, but that should be left out
of this discussion.

Regardless of your theorization I must congratulate you for the wonderful
experiment that should be known by your name.
In the history of science thousands of scientists have contributed to the
bulk of experimental data.
Yet few make it to the top including Clowns like Einstein.

With best regards.

EL Hemetis

Thank you for these words, they show me that some people at least are not
shackled to the powers that be.
Your integrity is admirable.

Kind regards

Andrew
 

Offline daveshorts

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Re: How do Trees Really lift Water to their Leaves?
« Reply #41 on: 28/04/2005 16:12:54 »
I don't see how the two quotes you have made strengthen your case, the first one just says that cohesion theory means that the experiment that you have carried out is possible, the second one is an extract from this thread:
http://www.the-tree.org.uk/MessageBoard/thread.php?id=53&pos=0 which is remarkably similar to this thread, and E.L. Hemetis brings up most of the same critisisms as I have.
quote:
I have never seen a bowl of water at the top of any tree other than those left by the owners of apple trees to prevent scrumpers.

Of course there isn't!!! This is because the whole process is driven by evaporation concentrating salts and sugars in tthe leaf, which causes osmosis to suck water out of the top of the xylem, and then the cohesion of water means that the whole column is pulled up, so it sucks more water in at the bottom.
 So the water leaving the top is as a gas, so it won't fill up a bowl.

Just to make it clear, it is not water cohesion that is doing the pulling, but osmosis, cohesion just means that the water behaves like a wire, so if you pull the top water gets sucked in at the bottom.
quote:
In the case of a tree, we could place a plastic bag over a branch and collect and extract the condensed water in its canopy.

Exactly, because evaporation is providing the energy to lift water against gravity, so the water coming out of the tree is a vapour.
quote:
It is possible to design a model that can lift sea water, extract pure water and return the denser ballast to the sea through a tube in order to provide the pumping for the desalination. But I have long since given up jumping though loops to amuse people.

It isn't to amuse people, it is to address what is the fundamental challenge to your hypothesis. The experiment in Brixham didn't lift more water than it dropped down. A tree lifts 50 times more water up the xylem than comes down the phloem.

 It takes one joule of energy to lift 1 a kg of 1 metre. A litre of water weighs 1kg a litre of sap may weigh 1.5kg (a generous estimate). The litre of sap falling 10m will release 15J of energy, this is enough to lift 1.5l of water back up the 10m. However a tree lifts 50l of water etc. up a tree this means that you need to get 48.5J of energy from somewhere. In the conventional model this energy comes in the form of heat evaporating water at the top of the tree. Where is it coming from in your model.

If your model can do this with no other energy inputs there would be a lot more interest in it than just from plant biologists as you would have built a perpetual motion machine.
 

Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #42 on: 28/04/2005 16:32:36 »
One only needs to show the method of circulation. Evaporation is an inevitable consequence of water flowing through the massive surface area of a tree.

Evaporation with a plastic bag over a branch? maybe water oozing from the leaves is a more likely explanation. Evaporation requires a dry air, suns energy and wind. High humidity shuts down transpiration (common knowledge) The environment inside the plastic bag would be near 100% humidity. So where does your accepted without question theory address this :) Mine fits with it like a glove.

Maybe you would like to explain how evaporation from the trees leaves can alter the concentration of solutes at an elevated point, and gravity does not affect the flow of these concentrated solutes. I wait with bated breath



Death is natures way of telling us to slow down.
 

Offline daveshorts

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Re: How do Trees Really lift Water to their Leaves?
« Reply #43 on: 28/04/2005 17:08:19 »
quote:
One only needs to show the method of circulation. Evaporation is an inevitable consequence of water flowing through the massive surface area of a tree.


If evaporation is driving the process, you do not need a downward tube to lift water up the tree! If evaporation is not putting in the energy you need to get energy from somewhere for your hypothesis to work.

There are phloem in a tree, but they are not needed in order to lift water up.

quote:
Evaporation with a plastic bag over a branch? maybe water oozing from the leaves is a more likely explanation. Evaporation requires a dry air, suns energy and wind. High humidity shuts down transpiration (common knowledge) The environment inside the plastic bag would be near 100% humidity. So where does your accepted without question theory address this :) Mine fits with it like a glove.


The definition of 100% humidity is that water will condense at the same rate as it is evaporating. So for some evaporation you either need a humidity of less than 100% or the leaf to be at a higher temperature than the air (if you boil a pan of water it will still evaporate, even if you are in a room at 100% humidity), which it will be on a sunny day. So what is happening in your bag is the water is evaporating from the leaves which are hot as they are a dark colour and condensing on the plastic bag which is cooled by the external air.

If the water was oozing out of the leaves and not evaporating this would bring up the problem with energies I mentioned earlier.

quote:
Maybe you would like to explain how evaporation from the trees leaves can alter the concentration of solutes at an elevated point, and gravity does not affect the flow of these concentrated solutes. I wait with bated breath


The solutes are in cells and therefore behind cell membranes which are impermiable to the solutes. As Rosy mentioned earlier a cell has to use energy to pump large molecules through a cell mambrane.
 

Offline rosy

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Re: How do Trees Really lift Water to their Leaves?
« Reply #44 on: 28/04/2005 17:09:41 »
So, guys, do we know what *does* happen when you tie a plastic bag to a tree?? I'd expect it to reach a certain humidity level (higher than atmospheric) within the bag and then even out.

You would possibly then find that the leaves started to release xylem sap, by pumping ions across the cell membrane (and energy-expensive process) and allowing water to follow them. Also via a transport protein but not (this time) one which requires energy to function (I'm a bit hazy here, and my cell biology notes are 60 miles away, but that's the gist).

From http://plantphys.info/Plant_Physiology/transpiralec.html
quote:

Root pressure is also sometimes visible on leaves. Under conditions of high humidity, cool temperature, and low light exposure root pressure can push xylem fluids through leaf mesophyll and out some larger pores in the leaves called hydathodes. Thus on a cool morning as you walk across the grass you notice a drop of liquid on the tip of each blade. You may have thought this was dew, but because it is on the upward pointing tip, you realize that this cannot be so. A test of solutes would demonstrate that this is xylem sap, not condensed humidity! The process by which this exudes is called guttation and it is driven by root pressure.


I don't know how much plant physiology/cell biology you've studied, so forgive me if I'm teaching my grandmother to suck eggs... Plant cell membranes are impermeable to sugars such as sucrose. Transfer of sugars from cell to cell, as in the phloem, occurs only when the cell "chooses" to expend energy on the process. Thus, except where sugars *are* being moved about by active transport, there essentially isn't a "flow of concentrated solutes" to deal with, any more than there's a "flow of cells".
 

Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #45 on: 28/04/2005 22:18:29 »
Dave, ever thought about becoming a politician?

Please read
standard GCSE text books entitled GCSE BIOLOGY, D.G. Mackean. ISBN 0-7195-4281-2 first published in 1986.

Posted earlier

To state that solutes and sugars stay put and are not acted upon by gravity is absurd! How do we tap rubber, harvest amber and maple syrup?????? There is an obvious downward flow!!!! And for every action there must be a reaction !!!!!


Please repeat the simple experiments, or give me an address and i will personally come to you and set them up so that you can see what exactly we are talking about here.

Andrew
 

Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #46 on: 28/04/2005 22:21:25 »
Rosy, my point is that accepted explanations for bulk flow are erroneous, and do not account for this amazingly simple, yet hitherto overlooked paradigm

Andrew

Suck it and see
 

Offline rosy

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Re: How do Trees Really lift Water to their Leaves?
« Reply #47 on: 28/04/2005 23:53:01 »
quote:

To state that solutes and sugars stay put and are not acted upon by gravity is absurd! How do we tap rubber, harvest amber and maple syrup?????? There is an obvious downward flow!!!! And for every action there must be a reaction !!!!!



Maple syrup is quoted on various websites as being an anomally in that it is harvested from the xylem and has a concentration of sugar as high as 2%. This is given as a remarkably high concentration not normally found in the xylae.
Presumably to make the syrup we're familiar with as a pancake dressing they have to boil it up a bit ;)
We don't harvest amber, it's a fossilised form of tree resin.
Sap and rubber are secreted by trees in response to injury.
Rubber is not part of the tree's transport system at all.
From http://www.worldwildlife.org/bsp/bcn/learning/primer/impacts.htm
quote:

It is useful in this context to briefly examine the physiology of rubber production by Hevea trees. Rubber latex is manufactured in special cells using stored carbohydrates. In addition to rubber, the latex contains proteins, sugars, tannins, alkaloids, and mineral salts. Although the exact biological function of this rich concoction is unknown, biochemically it is very expensive for the tree to produce. The abundant production of rubber latex by Hevea trees is an abnormal response to injury--a tapped tree produces hundreds of times more latex than it would have formed had it not been tapped. The net result is that commercial tapping regimes cause the tree to divert a considerable proportion of the resources normally used for growth and reproduction to the production of rubber.


Resin (the sticky stuff that you see on the outside of, say, pine trees when they're injured) is a defence mechanism rather than something involved in bulk flow.

Everything acted on by gravity must by definition go downwards?
Really? Even if it's on top of something else? I don't usually find myself going through the floor into the basement. The sugars are on top of an (impermeable, to them) cell membrane, so there's no reason why they shouldn't stay put.
 

Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #48 on: 29/04/2005 10:03:21 »
Rosy
http://instruct1.cit.cornell.edu/courses/biog105/pages/demos/105/unit5/cuttreephotos.html
Your statement about maple syrup merely serves to highlight that the flow and pathway of sugars can be reverted under certain environmental conditions, namely late winter, in which it is currently thought that the cold nights cause co2 gas bubbles to form due to the hydrolysis of starch, which expands during the warmer daytime altering the pressure in the xylem from negative to positive.
This is precisely why sugars and minerals are found to be more abundant in the roots of deciduous trees during the fall.
I have also mentioned this in my paper, as pressure changes are observed in the xylem when cavitation occurs, or when the leaves cease to function of fall in autumn. Fits perfectly with the new paradigm.
Amber by the way is Harvested in Poland and the Ukraine to make ornaments and jewellery, it is also heated up to form shapes in moulds, while retaining the trapped insects, although this often fragments the insects, whereas naturally formed amber maintains the insects perfectly.
Under normal transpiring conditions, the sugar pathway and flow is in the phloem. But as you state, it is harvested when the water transport is suppressed by winter.

Yes even if its on top of something else! Take a look at the flow of dense rock pulled towards the Earths core. Keep eating the doughnuts and you might find yourself on the basement floor.


"The explanation requiring the fewest assumptions is most likely to be correct."
K.I.S. "Keep it simple!"
 

Offline rosy

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Re: How do Trees Really lift Water to their Leaves?
« Reply #49 on: 29/04/2005 13:38:40 »
My apologies, the structure of this post may be a little confused as I had to go to a class part way through writing it and haven't time to start from scratch and make it into comprehensible prose(!!)
I think I've made all the points I intended to, however!


If the primary system for moving water up trees is this convection type system you're proposing, how do the sugars get *up* the trees to the ends of the branches for leaf formation in the spring? According to your model, if there aren't any leaves yet how does the flow get started and worse how does it draw more sugars (and amino acids and whatever else it needs) up than it drops down (which it must in order to construct new leaves)? It's got to use active transport in the phloem.

OK, my understanding of the current model (and I'm in no sense a plant scientist).
In the leaf cells, sugar is produced and water is lost by evaporation from the leaves.
Sugars are transferred by (mainly passive) transport (depending on the concentrations) into the phloem. Given the sugars are already (since they're made in the leaves and moved to other parts of the plant) moving down a concentration gradient, there is no reason for more water to follow them across the cell.
Loss of water from the leaves results in water being drawn up from the roots via the xylae(osmosis).
The sugars want to move to a position of lower energy/higher entropy (and so to places where there is less sugar already). There *is* an energy gain in going downwards, yes, but as Dave points out it isn't actually very big if you're losing a whole load of water at the top. Your Brixham experiment depends on using the weight of the water coming over the top of the loop to draw the water below it up. In order to produce any energy at all the salt/sugar solution has actually to move downwards, which in your model it can't do unless the water which it pulls up follows it straight back down the opposite tube. Indeed, as was pointed out by EL Hemetis, there is before us the evidence of plants quite happily growing with their leaves below their roots. I'm far more convinced by the idea that that concentration effects dominate.

Where is the need for a "simpler" explanation? The current model doesn't strike me as any more complicated than yours (and you have yourself shown that provided there's a sufficient upwards "pull" water can sustain the "tension" required), given that the mechanisms I've outlines are undoubtedly present in generalised cells and therefore presumably in trees.

Amber really is just the fossilized stuff. The "amber" people harvest is probably copal, which I *think* is a form of resin.
http://www.emporia.edu/earthsci/amber/copal.htm

Also, the falling through the floor thing... if I eat too many doughnuts I may fall through the floor. But only by breaking the floor. The only way of applying the same argument to sugar solution is to say that the sieve plates between phloem cells rupture. Which is OK unless the tree's ever going to want to move nutrient solutions "uphill", which is going to require (energy expensive) active transport because as you so rightly say, all other things being equal heavy solutions (and indeed rocks) want to move downwards with gravity *if the thing they're resting on can move out of the way to allow this*.
 

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Re: How do Trees Really lift Water to their Leaves?
« Reply #49 on: 29/04/2005 13:38:40 »

 

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