How do Trees Really lift Water to their Leaves?

Reply #80 on: 09/05/2005 18:26:47 »
I'm going to move this thread to the 'cells' forum shortly, so look out for it there...

TNS

Why are you moving the thread? As this is a physics discussion, Can you please enlighten me why you believe it belongs on the cells forum?

Andrew

Dave:
Although most of the discussion has been on physics, the question is actally biology, and a lot of the evidence is microscopic.

I beg to differ David, None of my experimental models are microscopic. And yes, most of the discussion is on physics. The movement of fluids, fluid dynamics.

A Decisive Step: 1889–1924
The crucial period for our current views on the mechanism of water transport in plants were the years between 1889 and 1896. As a cornerstone we have a monumental book, Eduard Strasburger´s Über den Bau und die Verrichtungen der Leitungsbahnen in den Pflanzen (On construction and function of the conduits in plants) written in 1891. Strasburger, who is mostly remembered for his outstanding contributions to plant cytology, gave an encyclopedic compilation of old and recent work done on pathways and mechanisms of water transport in the plant body. As Sir Francis Darwin stated in 1896: "It is difficult to praise too highly this great effort of Strasburger´s".

Strasburger himself was an adherent of the school of physics and provided some strikingly efficient demonstrations of water being lifted to considerable heights without any involvement of living cells (Figure 1). He showed that woody stems with their lower end immersed in concentrated solutions of copper sulfate or picric acid and severed by a cut made below the surface of the liquid, will readily suck the solution up. Immediately upon contact, the poisonous fluid kills all living cells in its way, but the copper or the acid arrive in the transpiring leaves and kill them as well. The uptake of the solution and the loss of water from the dead leaves may continue for several weeks, and new solutions of a different color may be lifted in a dead stem.

Dave: We have been through this before, but this is true of the xylem and water will be drawn up a dead tree, but not of the Phloem which is a complex bi-directional sugar and mineral transport system, not the downwards only pipe that is needed for your theories.

There goes your precious leaf generated tension theory. All of the cells were killed by the acid / copper sulphate solution. All of them! That means the phloem and the xylem. Yet the flow to the leaves remained functional for 3 weeks. Explain that using the cohesion theory!

There goes any connection whatsoever with living plant cells.

All we are left with is some dead inanimate tubular conduits and pits, “sounds like my tubular experiment more than some wonderful mystical suction from dead leaves”? Add some salts at the top of the tree from the decay / breakdown of the leaves, which will alone generate flow according to my theory.

I know, I have repeated the experiments with liquidised leaves, tea, milk, urine, etc etc. anything denser than water will initiate this flow and the sooner scientists accept that this flow will occur wherever there is a denser solution above a less dense solution the better.

But to hide this thread from the view of people who are interested in physics and fluid dynamics is nothing short of censorship at best!

The truth of the matter is that this new paradigm looks a damned site more likely than anything that has gone before it! And it has already generated a lot of interest.

Are you afraid that it is becoming too popular? And feel the need to suppress it by confining it to the cells, behind bars so to speak?

This theory is innocent and should not spend one night in the cells!
Andrew K Fletcher

Dave:
With physics it is always a good idea to keep an eye on where the energy is going,
So just answer me this...98% of the water that goes up the tree is evaporated, so for every 100kg of water going up the tree at the most 2kg of water comes back down.

lifting 100kg of water 100m takes 10 000J dropping 3kg of water and sugar 100m releases 300J

where does the other 9700J come from?

Rosy:
quote:But to hide this thread from the view of people who are interested in physics and fluid dynamics is nothing short of censorship at best!
...and *that* is nothing short of paranoia at best.
It is a slightly odd feature of this site that it doesn't have a more general "plants" section but no-one doubts that your results physically occurred in your tube experiments, that the weight of the solution is causing the flow.
Anyone interested in how plants work will be interested in cells too, and will be looking at that part of the website too.
If you're that worried you could always post a new thread solely about the physics of your demos... maybe even with a little more explanation of how your ideas accord with things like the principle of conservation of energy (unless you're ruling that out too? I haven't worked that out).
You could even explain the principles by which (on about page one) you reckon you can get water at the top of your loop given that the water in it must be a negative pressure.

you don't have to be a genius to see that the cells forum is hardly visited by anyone, whereas the general science section is visited by most of the people who use the forum. Nevertheless I thank you for seeing the logic in the experiments and for not doubting their validity as viable repeatable experiments.
Andrew

@ Dave
The beauty of this simple experiment is that it shows circulation of fluids through conduits. Inside the dead tree that is still lifting water and evaporating it from the leaves, all we have is the knowledge that circulation must be taking place because the leaves are still transpiring moisture and that has to have come from the soil!

If only 1 gram of denser saline solution was returned in either a xylem or a phloem, this circulation would effortlessly lift / circulate many thousands of times its own volume, providing the tree with ample water to continue its evaporation. However, when the tree has been killed, the production of sugars will come to an end eventually and the minerals will find their way down to the lower part of the tree, ending the circulation at the end of the three week period, leaving only heat generated density changes to continue.

The cohesion theory needs to show this erroneous one-way lift of water. My theory requires the water to circulate. If you could set up the experiment you would see how important this is.

1 gram triggers this flow, never mind 2kgs.

Yesterday evening at 11.25pm, I set up an experiment with a 4 metre length of tube, open at both ends and filled with boiled water. At the time I am posting this, no cavitation has occurred, meaning that the water inside the tube requires only that the tubes be held in a vertical position, as they would predominantly be if they were inside a tree. This alone raises a serious question about your energy analogy.

So unless you are referring to the 10 000J as the suns energy, it does not relate to the experiments. 1 gram can cause many thousands of times its own volume to circulate vertically, and this will inevitably cause horizontal or diagonal circulation, depending on the route with the least resistance.

All that is needed is to show how the water circulates. Note the word circulates, as it is important. The term lift relates to your current line of thinking.

Dave:
You are right you can cause lots of water to circulate without using much saline in your experiment, this is because you are not increasing the average height of water in the system - the energy required to lift the water on the up side is exactly the same as the energy released dropping the water on the down side. You are just moving it from one bottle at the bottom to the other. This means that all the weight of the saline has to do is overcome friction.

However a tree is not circulating at least 98% of the water!!!

98% of the water going up the xylem leaves from the leaves (you quoted this figure several pages ago) it isn't coming back down so the energy to lift it up is not released by water going down the tree.

So where is this 97J/kg coming from in your model?

Reply #92 on: 10/05/2005 17:29:02 »
I have tried to convince you that the diameter or even the number of upward flowing water beeds does not equate to the volume of water or the diameter of tube in the return flow.

I have stated before, that you can have a larger bore tube on one side of the loop and a smaller bore tube on the other side, the balance is equal and the water is held in suspension.

I have tested this using a twin tube on one side and a single tube on the other, at 3 metres height. The balance on both sides is equal with no net flow either way. Only when a tiny amount of salt solution is added to the single tube side, or for that matter the double tube side does the circulation begin.

At the top of the tree the bore sizes change as the branches taper of to twigs, meaning that the return flow will inevitably be in a smaller tube to start with. As the water evaporates from the fine bore tubes, it is left with the return flow being directed down tubes of a similar size, or if that pathway cause back pressure, the flow will find a new route, causing more tubes to form.

So if you can picture a large volume of water being drawn through smaller tubes and that this reduced but denser volume flowing down through the smaller tube is sufficient to generate the pull of higher volumes of less dense solution in larger or even multiple tubes rising up, it simply does not require the energy input you are presuming it needs to flow. All I keep asking is that you repeat the experiments, or let me repeat the experiments and you will see exactly what I am talking about.

Hand the experiment over to the people at your homepage and ask them to form an opinion about whether this is relevant to plants and trees. I have not yet failed to convince all that have witnessed the experiments.

You also mention about the heights that fluids have to continuously attain, if I am not mistaken by your post. There is another force at play in this experiment, and that is the increased head of water generated in the rising side of the tube. The Brixham experiment dos not exactly reflect the fact that all of the multi-conduits inside a trees structure are inside one big conduit, and the roots are not exactly open as my tubes are.
Enclosing my experiment inside a tube filled with water would produce a net increase in the head of water, showing how trees can grow higher than the original water levels. It also shows to perfection how dew exudes from grass in the morning and how water exudes from a cut stem, previously believed to be some mystical force generated by the roots, known as root pressure.

@Chris,
Why does this thread have to be moved? We have agreed that it crosses the boundaries of Biology, Physics and even Chemistry.
It also crosses the medical and physiology boundaries, geology and palaeontology and even evolutionary boundaries.
If this is not general science then what is?

Dave:
If you connect a large tube and a small tube together in teh way you suggest it will work, however water is not being gained or lost from the tubes, so the flow in litres/second will be the same in the big tube as the small tube, the velocity in the big tube will just be slower.

The down bottle fills up by the same amount as the up bottle empties doesn't it?

If the up pipe is 12mm and the down pipe is 6mm, to test this colour the saline red and the water in the up bottle blue you will see that when the red drops all the way down the pipe the blue will lift up about 1/4 as far as the saline drops. so you have lifted 4times as much water 1/4 of the distance as the saline dropped - so overall water has just moved from one bottle to another.

A tree lifts water to it's leaves ans 98% of it evaporates, your model lifts water to the top then all of it comes back down. The two are not equivalent at all!!!
I am the people at my homepage so that won't really help - and at no point have I argued with the results of your experiments just your interpretations of them, so doing the experiments wouldn't necessarily help, although I would be happy to come and see yours at some point when I am in Devon and not too busy.

NO David, if the tree is killed and the flow continues for another three weeks, it definately is not the tree that is lifting the water!

But you are missing my point with regards to this flow in a tree. The very nature of the trees construction enables transpiration to take place. I would not even know where to start trying to make an artificial tree. But killing the tree and the water / sap inside it is still flowing for 3 weeks is a vertual artificial tree.

If saline solution were to be some how introduced at the top of the tree once it has stopped flowing after the three weeks, we should observe fresh circulation due to the initiation of said flow and return system. Obiously, we would have to refil the tree to its previous levels of water to replace the losses from the falling levels of water inside the tree.

Give me a date, and I will drive to Cambridge and give a demonstration for all to see.

Andrew

Moth:
Reply #96 on: 11/05/2005 10:07:08 »
Andrew, I too met you in Brixham with CHaOS (yes we are ganging up on you , so have had some time to think about your idea.

I believe your experiment works, but i mostly disagree with the conclusions you draw from it and the arguments you use to explain it. I also disagree with your dismissal of the other princples involved.

I imagine that there could exist a tree which transpired very little, but instead used your salt-siphon principle to create a vertical conveyor-belt of water to transfer chemicals between its roots and leaves. Dilute solution would rise up one set of tubes while an equal flow of denser, more concentrated solution would fall down another set of tubes, and at either end living cells could maintain the concentration difference by extracting solutes at the bottom and injecting them at the top. I'm sure this does some violence to a biologist's understanding of trees (and i know it doesn't match mine), but as a physicist i am happy with it in principle.

I consider it an interesting and clever idea, but don't believe it has much to do with how real trees actually work. The key flaw is that the salt-siphon cannot explain transpiration. Your idea requires almost equal up and down flows, while transpiration means that (vastly) more water flows up than down.

You rubbish root pressure, saying that if it worked then jets of water would squirt from the roots of felled trees. I don't think that follows. Water is almost incompressable at the pressures we are discussing, so it is entirely possible for the roots to contain water at a significant pressure without causing them to squirt when cut as the water would need to expand only a tiny amount to completely relieve the pressure. What i would expect as evidence for the existence of root pressure is for roots to gently ooze liquid for some time after they are cut. Indeed this is what i have observed: when I have cut limbs from trees during the spring and summer i have often seen liquid flow from around the edges of the wounds (where the current year's phloem and xylem are). To be clear, i'm not prepared to swear root pressure is all there is, but i don't find you dismissal of it convincing.

Osmosis is a complex, subtle and powerful phenomenon. It is quite possible that the widespread explanations of it are faulty, and yet osmosis really happens. I found this paper which discusses the many ways of analysing osmosis: arxiv.org/abs/physics/0305011

Your recent answers to Dave's questions about the energy budget refer to differing sizes for up and down tubes. This is strikingly similar to a perpetual motion machine I invented when i was 14. It works like this: construct a siphon from a short fat tube and a long thin tube connected at the top. Place the bottom ends in buckets and fill the system with water. As there is a greater weight of water in the fat tube it will pull water up the thin tube, so transfering water from the lower bucket to the higher one. I hope you can see why this doesn't work, and why your replies don't answer Dave's question.

I don't buy your dismissal of the 'conected water column powered by evaporation at the top' idea, but i want to do some calculations before i post on that subject.

You seem to attack most things simply by saying they are implausible. This is not an argument that holds any weight with me. If you want any acceptance of your idea you will have to start making sense in terms of accepted scientific priciples. Our discussion in the E=mc^2 thread suggests that you are not prepared to do this, but i still hope you will. It is as if we are speaking different languages. I have not managed to learn yours from your postings here, so if we are to be able to communicate you must learn mine.

I would be interested in seeing your experiment, but even if it works exactly as you say it does it wont change my opinions of your explanation of it. Mostly i am just curious about the details of your method, and would rather see it for my self than through your discription.

I suggest this thread remain in General Science - the subject is a mix of biology and physics with a hint of chemistry. The discussion has lacked biologists so far and could certainly benefit from their input, but while Dave and I continue to examine the physical basis of Andrew's theory it would be out of place in the Biology section.