How do Trees Really lift Water to their Leaves?

Why is it that the phloem sap is observed to flow down, in the opposite direction to the predicted path of suction generated by the leaves? According to this theory, it is hard to understand how a plant or tree can differentiate between the xylem and the phloem. How can the same leaf suck up water in the xylem and blow it down the phloem at the same time? If you were to place an atomiser from a paint spray gun at the top of the tree, under say 65 psi, would you really expect this to cause water to be drawn up the tubes inside the tree? NO! It simply cannot work any more than a lift pump would work placed at the top of the tree. Why would you expect the current cohesion theory to work? You add, well there are many leaves at the top of the tree and the interactions between all of the leaves and the atmosphere would suffice to generate ample pull. How? There are many trees which have minimal leaves at the tops, like the larch which lift water with ease, yet do not have anywhere near the surface areas that you suggest would be required to generate the pull! Let alone Strasburger’s dead transpiring trees.

Even if you removed even more branches from the top of a larch it would carry on pulling water to the top! Look at bamboo for instance, or climbing vines.

A few days ago I went out with a stethoscope to listen to the trickling of sap as it flows in bulk within the trunk of an ash tree, which was just in bud. Again this tree did not have the massive surface area the cohesion theory requires of it. I could hear the water flowing and the cavitations creating cracking noises.

Now explain that with your knowledge of physics please,

Rosy:
On the "Gentleman Scientist" question...
There is no particular reason, I don't think, why a "gentleman scientist" such as Andrew shouldn't be able to make and interpret accurately useful new discoveries many fields (I'd suggest that this wasn't infact the case in quantum physics which tends to require several miles of subterranean tunnels full of particle accelerators as this might be more than a little way outside the typical spare-time budget). It would require a phenomenal amount of dedication to get up to speed on the current thinking, getting hold of material not available on the internet etc., but some do have that.

However... the presumption within the scientific community is that individuals not doing this as a full-time job can't possibly have the time, energy and access to materials this requires, and so tend to be starting with an assumption that such people are unlikely to have anything very interesting to say. The primary necessity for anyone from an unexpected background who wanted to get their theory recognised by the scientific establishment is to write a *very* detailed explanation of their new theory along with a discussion of the old theory they're attempting to debunk which shows a very thorough understanding of the old theory such that it's impossible for readers to discount the whole exercise by saying to themselves "he only doesn't believe our theory because he doesn't understand it".
You haven't persuaded me yet. This may be because we're attempting to communicate in text and you haven't shown me any numbers, but I'm not convinced.

What I do find surprising is that no one here appears to have conducted the experiments for themselves in order to give a qualified account of their own observations. If it is the money, I will send the £3.00 so that you can purchase the tubing and T junctions.

Nope, not the money. The time. And the space. When I have more than a couple of hours together to call my own I have every intention of having a shot at some of your experiments. But as a student in a ground floor room in the middle of a seriously flat county this is not high on my list of priorities.

If you were to place an atomiser from a paint spray gun at the top of the tree, under say 65 psi, would you really expect this to cause water to be drawn up the tubes inside the tree?

I don't know how an atomiser from a paint spray gun works, but if it didn't introduce an air bubble or a nucleation site for a cavitation into the system I'd expect any given pressure to draw up a column of water of the corresponding depth... 1Atm vs a vacuum pushes water up 10m, as in a water barometer so my expectation would be that provided no cavitation occurs (and I'd suspect most conventional pumps in this area) a negative pressure of 2Atm would pull water up about 20m.

Why is it that the phloem sap is observed to flow down, in the opposite direction to the predicted path of suction generated by the leaves?

Andrew fluid flows in the Phloem up down and sideways, it has been measured to be at a positive pressure - THIS MEANS IT CAN'T BE SUCKING UP THE WATER IN THE XYLEM DIRECTLY!! in order to suck the pressure in the phloem must be lower than the xylem..

If you read my previous post you would have found out that the reason it is at a higher pressure than the xylem is osmosis - the Phloem is sugary, and therefore water will osmosis into it from the xylem. This can happen at pressure differences of 10-20 atmospheres quite happily.

If you were to place an atomiser from a paint spray gun at the top of the tree, under say 65 psi, would you really expect this to cause water to be drawn up the tubes inside the tree?

If you made the atomiser out of something hydrophilic like paper or cotton and the holes in are small enough then yes.

Andrew HOW DO YOU KNOW WHAT AREAS ARE REQUIRED FOR THIS TO WORK? have you done any experiments or even calculations to find out - if so could I would be interested, if not please not don't make broad generalisations which you can't back up

@ Dave
If you had read my previous posts, you would have found that this flow is not pressure dependent! It does not require pressure; it generates pressures as it flows! The tiny pulses of saline solution injected at the top of the loop experiment flow down. This causes a dragging effect because of the cohesive qualities of water. The downward flow cannot flow down without dragging water down with it. It behaves like an elasticised string. I.E. the downward flow is not possible, without it causing an upward flow! Phloem flows in the direction of a sink! If that sink happens to be an apple, then it will flow towards the apple, if it happens to be a root, it will flow to the root. If a denser solution is flowing down, then a less dense solution will be flowing up or in any direction affording less resistance! Hence “Flow and return”. In my inverted tubular experiment, both tubes are under a negative pressure with no saline added. Demonstrated by the water retreating up the tubes when the tubes are lifted out! Yet when the saline is added, it causes the contents of the whole tube to rotate in the direction of the downward flowing salt solution.

1. Evaporation cannot take place without it altering the density of the sap at the leaf!
2. Gravity will pull on the denser sap causing it to flow in the direction of a sink!
3. The denser sap will drag less dense solutions from other areas of the tree!
4. Pressures will be altered by this flow and return system, but the flow itself is not pressure dependent. I.E. Pressure changes are not required to cause this flow in any direction, other than the effect of gravity upon dense sollutions!
5. The flow and return will generate negative pressures and tension in the sap at the roots and throughout the xylem it will generate an upward pull on the water, which will cause water to flow horizontal, down, up and diagonally, because the water is being dragged upon by the falling solutes and in the phloem it will inevitably change the negative pressure to a positive pressure, causing both a pushing force in front of it and a pulling tension behind it.
6. In the tree, there is an outer sleeve, which adds additional support for this flow and return, making it much more robust than the simple inverted U tube experiment. Within this sleeve / bark cavitations can occur frequently and do not interfere with this flow and return system. The sap simply flows around the gas bubbles, as observed in my own tubular experiments.
7. In these tubular experiments, it was also observed that a two-tier flow system can exist in a single tube, meaning, that there is a flow and return observed in the same side of a closed loop of tubing. Meaning, that a concentrated solution flows down one side of a diagonally placed loop of tubing, while clean water flows above it in the opposite direction!

For you to keep dismissing this as irrelevant to trees, without observing the hard evidence for yourself is a reaction I have grown to expect from people who would rather believe text in text books, than to question and evaluate the theories for themselves. You have absolutely no idea of the full implications. I have lived and loved my work and will do so until the day I die!

I therefore decline your polite invitation to become self gagged and hope you will understand why.

Andrew

Dave:
Yes your system generates it's own pressure differences however the water is still moving because of pressure differences they are just generated by density differences not by a pump..

Shall we do a little calculation...

if you inject 20cm of saline with a density of 1.5g/cm3 this will produce an extra pressure of about (1000kg/m3-1500kg/m3)*.2m*9.81 = -1000Pa or -.01Bar above the saline on the downwards side.

So for a little overview:
The pressure at the top of a 20m tube on the no saline side is -1Bar
on the saline side it is -1.01Bar because of the extra weight of the saline pulling on it.

This means that at the top the pressure on the saline side is lower so water moves towards the saline side - as you have observed.


However if you measure the pressure of the fluid in the Phloem
www.pubmedcentral.nih.gov/pagerender.fcg...d=440496&pageindex=1
you find the pressure is positive and up to 10 Bar - (otherwise aphids would implode)

So lets think about this -

the pressure in the xylem is at up to -10Bar the pressure
in the Phloem it is at +10 Bar.

Now you are expecting me to accept that the water is moving against a pressure difference of 20Bar to flow into the Phloem with no Osmosis going on...?

For you to keep dismissing this as irrelevant to trees, without observing the hard evidence for yourself is a reaction I have grown to expect from people who would rather believe text in text books, than to question and evaluate the theories for themselves. You have absolutely no idea of the full implications. I have lived and loved my work and will do so until the day I die!

Please do not say that I am ignoring the hard evidence - at no point have I said that there is much wrong with your experiments - they are exactly what I would expect to happen apart from a few minor details that you have not investigated in detail.

What I am disputing with you is your interpretation, as although on the surface it sounds nice if you had bothered to do any simple calculations - like how much energy is released by the sap going down compared to the 50x more water going up, looked at the actual structures in a plant, considered what the pressure is in the Phloem, considered that sugar flows in more than one direction in a plant, etc. you would have realised that unless a tree is a perpetual motion machine, and is not designed the way it appears to be it can't work the way you describe.

The most important question I have to you despite all this, is have you ever considered that you may be wrong? or preferably tried to prove yourself wrong. As if you haven't you are not doing science but PR.

Inside a phloem, the structure adds an additional restrictive force on the downward flow, mainly friction, causing the falling solutes to back up, “Hydraulic brake”, slowing the flow down, and allowing sugars and salts to accumulate, giving rise to higher pressures. Inside the tree, as previously explained, there is additional support for the columns of water, due to the outer sleeve of the tree. This will inevitably explain the reductions in negative tension found inside the tree, as opposed to those that are obvious inside the Brixham Experiment. For instance, If I were to use a closed loop of tubing instead of the open ended tubing in the Brixham Experiment, then the height that can easily be obtained would exceed even the tallest of trees, and the circulation generated by the solutes would effortlessly rotate the fluids in the direction of the density path. Again the support of either a closed loop or a semi-closed loop changes the pressure parameters greatly.

In your calculations, I have difficulty understanding how you have derived the figures.

I believe you will find that the negative tension inside the inverted U tube at 20 metres will be far higher than your estimate. And as you are aware, the experiment is designed to demonstrate the flow, not to mirror the internal structure of a tree. So comparing like for like with the inverted tube is pointless.

See Reference to Professor H.T.Hammel letter page 2 of this thread.

The most important question I have to you despite all this, is have you ever considered that you may be wrong? or preferably tried to prove yourself wrong. As if you haven't you are not doing science but PR.[/quote]

With this last question, it would appear that you are trying to belittle me. Why is this? Do you not think that given all of the years I have been working on this, I have not tested and re-tested as to whether I am correct or incorrect?
E.G.
One simple test for you:

Measure the density of your urine, making a note of what you have eaten and drank during the day. Retire to bed, and measure the density of your urine when you relieve yourself in the morning.

Now elevate your bed by no less than six inches or fifteen cm’s at the head end and repeat exactly as the day before.

Then sleep with your head down and your feet up on the same incline and do the same. Now compare the figures and explain why there are massive differences in urine density.

Also, if you have varicosity in the lower limbs, you might find that the veins are pulled in by the reduction in pressure inside the veins, as we did when sleeping with the head end elevated for four weeks. Strange, because the vein in my wife’s leg had been bulging and aching for 16 years, following the birth of our first child. The vein is no longer varicose and barely visible!

You will find that your heart rate will reduce by 10 to 12 beats per minute, and your respiration rate will reduce by 4-5 breaths per minute, even if you are a sleeping bull terrier! But you will need a partner to measure these while you are sleeping.

Most of my research since discovering this flow and return has been directed towards helping people suffering from a whole range of illnesses. Like I said before, this flow and return has no respect for where it flows, but flow it must! I have spent many years working with and helping people with neurological and non-neurological conditions, to which, I have never charged a single penny for my services.

However, discussing this physiology and its wide ranging relationships will only serve to complicate this discussion beyond the purpose of plants and trees, and I have absolutely no wish to do so, other than offering this as an excuse for not conducting a greater number of various experiments with water and tubes. I have found myself going full circle and addressing the foundations of the initial discovery, which is to show how the bulk flow is generated, how it circulates and how evaporation triggers it.

As for P.R. I have appeared on television 3 times, been featured in the Daily Mail, Western Morning News, BBC and independent radio, Woman’s Realm magazine, Herald Express, Sunday Independent, Disabled Bikers Magazine, Medical Physics Group Newsletter at The Institute of Physics. Why would I want to be doing P.R. on the Naked Scientists forum? I find this remark of yours a little terse.

I am here because I am trying to understand what is required of me to publish a paper that will provide the “Closed Shop Scientific and Medical Communities with a paper that is difficult for publishers and readers to ignore, and believe it or not, I am gaining a tremendous insight into how this is to be achieved. And perhaps enlist a little expert help.

Andrew

Rosy:
I'm not saying which is the right interpretation of the urine density experiment, but my first interpretation would be that if you sleep with your head raised it makes breathing easier, which means you sleep more deeply.
When you sleep you produce more of the antidiuretic hormone which controls water loss (or possibly re-uptake, I forget) in the kidneys, so that you lose more urea etc. and less water. I suspect (I fear there aren't any physiologists reading this thread, so I'll have to check it on the physiology forum) that if you sleep more deeply you produce more ADH and therefore urine is denser.
Which would mean that the result would be due to gravity, but rather due to an effect on snot than on blood.
I believe you will find that the negative tension inside the inverted U tube at 20 metres will be far higher than your estimate.


Atmospheric pressure will support a 10m column of water. This will give a vacuum pressure above the water (0Atm) We know that. (I think?)
Atmospheric pressure is about 10^5 Newtons per square metre.
Pressure due to gravity changes linearly with depth in a liquid. In a column 10m high which is in an open jar at the bottom will have a point 10m up where the pressure is 0 bar. You've established that water may but need not cavitate at negative pressures. If it does not then there must be a "pull" from above to support the extra weight of water in the column and the decrease in pressure continues linearly to be -1 Atm at 20m, -2 at 30m, etc, until caviatation occurs and the whole lot falls back to the 10m it can sustain without negative pressure.
The -1Atm pressure at 20m means that there is a pressure difference at that height between the outside atmosphere and the water in the tube of 2Atm or 2*10^5 kN per m2.

By the way, if you've had time to think about getting water out of your inverted tube at the top, which you reckoned a while back you could if you wished design an experiment to do, I'd still be interested to hear about it (or any time you do get time to consider it!)

@Rosy
Actually, you sleep less deeply with the bed inclined, rem sleep is less frequent, dreaming becomes far les frequent. The body generates a substantial amount of additional heat in the inclined position, avoiding the temperature drop off that horizontal sleep causes. More heat = higher evaporation, which inevitably results in the production of denser urine.
Head down tilt on the other hand produces urine of near water density! Which at least proves that renal function requires gravity in order to transport solutes through to the bladder. Head down tilt temperature also fits with the temperature reduction in hibernating bats, and as it is used to simulate the harmful effects of micro-gravity on astronauts, it has been thoroughly investigated, with huge amounts of literature available on the internet.

Dave:
Isn't REM sleep an indicator of light sleep - deep sleep happening in between the episodes of REM/dream sleep?

It may indicate that renal function is assisted by gravity, but it certainly doesn't proove gravity is required for solutes to be moved to the bladder. If it was the whole story then astronaughts would be dead after a few days in space...

It is possible that a lot of sleep problems could be assisted by altering the angle of the bed - this will have lots of effects like altering snoring, altering how hard the heart has to work, which will have lots of subsequent effects... the human body is a horribly complex system so making niave conclusions from simple experiments is a little dangerous