The Naked Scientists

The Naked Scientists Forum

Author Topic: How do Trees Really lift Water to their Leaves?  (Read 244929 times)

Offline BenV

  • Neilep Level Member
  • ******
  • Posts: 1503
    • View Profile
How do Trees Really lift Water to their Leaves?
« Reply #375 on: 13/11/2009 11:07:18 »
Sorry to jump back to my earlier example, but...

Are you saying, Andrew, that a man size flea would be able to jump to the same equivalent height as a normal size flea?

By ignoring the need for the maths, this is exactly what you are doing.

Once again, your own arrogance belies the fact that you have not done the work needed to prove yourself right - is it that you are too scared that you'll prove yourself wrong?

It certainly appears that way.

"Belief -based system" indeed.
 

Offline Andrew K Fletcher

  • Neilep Level Member
  • ******
  • Posts: 2331
  • KIS Keep It Simple
    • View Profile
How do Trees Really lift Water to their Leaves?
« Reply #376 on: 13/11/2009 14:04:58 »
The cavitations repair themselves, cavitations are taking place all of the time and emit lou8d cracking sounds. This does not result in the collapse of the circulation in the tree and this is where the problem with the cohesion tension hypothesis lies.

Have you any idea of how much pressure would be required to support the columns of water in tall trees using the cohesion T model? Do you not think that the leaves would literally become inverted under such immense tension or even sucked down the trees vessels for that matter?

Pete Scholander and Ted Hammel hit the nail on the head when they made the pressure bomb and began recording pressures far above those proposed and required by the CTT.

So ask yourself if this imaginary impressive tension is not present in tall trees how on earth are they able to conform with the rest of the theory?

Can you not see how absurd it is to propose that leaves can suck up water from the roots no matter how it is wrapped up?
 

Offline Andrew K Fletcher

  • Neilep Level Member
  • ******
  • Posts: 2331
  • KIS Keep It Simple
    • View Profile
How do Trees Really lift Water to their Leaves?
« Reply #377 on: 13/11/2009 14:17:50 »
Ben let us look at those maths in the Cohesion tension hypothesis first.
http://4e.plantphys.net/article.php?ch=&id=99
The application of the Ohm′s law to sap flow encompasses many phenomena (heat transfer, water transfer in soil, Darcy law, first diffusion law, etc.) and, it is therefore independent of the underlying physical mechanisms and the nature of moving fluid. For example, the electrical approach does not address whether sap is under tension or pressure. For this reason, the description of sap flow by Ohm′s is rather "phenomenological".

Had to look this word up: http://en.wikipedia.org/wiki/Phenomenology_%28science%29
Phenomenology in physical sciences

There are cases in physics when it is not possible to derive a theory for describing observed results from the known first principles (such as Newton's laws of motion or Maxwell's equations of electromagnetism). There may be several reasons for this. For example, the underlying theory is not yet discovered, or the mathematics to describe the observations is too complex. In these cases sometimes simple algebraic expressions may be used to model the observations or experimental results. The algebraic model is then used to make predictions about the results of other observations or experiments. If the predictions made by the algebraic model are sufficiently accurate, they are often adopted by the scientific community despite the fact that the algebraic expressions themselves cannot be (or have not yet been) derived from the fundamental theory of that domain of knowledge.

The boundaries between theory and phenomenology, and between phenomenology and experiment, are fuzzy. Some philosophers of science, and in particular Nancy Cartwright argue that any fundamental laws of Nature are merely phenomenological generalizations.


 

Offline rosy

  • Neilep Level Member
  • ******
  • Posts: 1018
  • Chemistry
    • View Profile
How do Trees Really lift Water to their Leaves?
« Reply #378 on: 13/11/2009 14:41:14 »
You keep on about how we're tied to the current explanations. Some of the other people you're talking to may be, I'm not. Indeed, I have little knowledge of how biologists (or indeed anyone else) explains exactly how trees work.

However, what I am interested in is the basic physics of this situation. You keep on, and on, and on, about how your macro experiments support your micro interpretations. All I'm saying is that they don't. Your experiments (certainly the ones I've seen), don't show diddly-squat of any relevence.

As you rightly say, what we "know" about science is quantified interpretation of experimentaly data and, often, there are gaps in exactly how far we can explain the origins of those quantitative relationships between this, that, and the other thing. And certainly much (or argualbly all) of biology falls into that category. On the other hand one of the most (possibly the most) tried, tested, and still undefeated bits of science is thermodynamics. In energetic terms, you don't get something for nothing. Just doesn't happen (or not anywhere so far demonstrated, anyhow).

Gravity just cannot provide enough energy from falling sap (even if we overlook all the other flaws in your arguments, which are many). So how do you account for that? If you can't account for it then your theory has no scientific merit at all. And I will carry on thinking you a deluded fool, not just for wasting so much of your time and energy pushing your dead-end assertions about gravity, but also for your abject failure to look for the real causes of your apparently successful inclined bed ideas. If your results in that are really are as good as you claim it's not only yourself you're failing by apparently trying your best to discredit them with everyone who knows one end of an equation from the other.

In other news, if leaves can't support the "suction" of a column of water below them, how exactly are the (if anything more fragile) root systems of these great trees supposed to support the colossal pressure above them?
 

Offline Andrew K Fletcher

  • Neilep Level Member
  • ******
  • Posts: 2331
  • KIS Keep It Simple
    • View Profile
How do Trees Really lift Water to their Leaves?
« Reply #379 on: 14/11/2009 08:57:59 »
Journal of Experimental Botany, Vol. 48, No. 315, pp. 1753-1765, October 1997
Journal of
Experimental
Botany
REVIEW ARTICLE
The Cohesion-Tension theory of sap ascent: current
controversies

Melvin T. Tyree 1
USDA Forest Service, Aiken Forestry Sciences Laboratory, PO Box 968, S. Burlington, VT 05402, USA
Received 12 February 1997; Accepted 21 May 1997
http://jxb.oxfordjournals.org/cgi/reprint/48/10/1753.pdf


 

Offline Andrew K Fletcher

  • Neilep Level Member
  • ******
  • Posts: 2331
  • KIS Keep It Simple
    • View Profile
How do Trees Really lift Water to their Leaves?
« Reply #380 on: 14/11/2009 09:02:38 »
Gravity does not provide the energy?

Gravity is the energy, gravity drives the sun, the weather and all of life on earth! Perpetually for now at least!

Gravity can raise a mountain to impressive heights, cause tidal waves that demolish coastlines, cause volcanoes to erupt, yet cannot influence solutes inside a tree or indeed a human? Bullshit!
 

Offline _Stefan_

  • Hero Member
  • *****
  • Posts: 814
    • View Profile
    • My Photobucket Album
How do Trees Really lift Water to their Leaves?
« Reply #381 on: 14/11/2009 12:57:57 »
Gravity is not a major enhancing factor in some of those things.

Also, aren't you making the fallacy of false analogy?
 

Offline Bored chemist

  • Neilep Level Member
  • ******
  • Posts: 8665
  • Thanked: 42 times
    • View Profile
How do Trees Really lift Water to their Leaves?
« Reply #382 on: 14/11/2009 16:33:42 »
"Gravity is the energy, gravity drives the sun,"
Just plain wrong.
Learn some physics and maths then come back.
 

Offline Madidus_Scientia

  • Neilep Level Member
  • ******
  • Posts: 1451
    • View Profile
How do Trees Really lift Water to their Leaves?
« Reply #383 on: 14/11/2009 21:37:36 »
Gravity does not provide the energy?

Gravity is the energy, gravity drives the sun, the weather and all of life on earth! Perpetually for now at least!

Gravity can raise a mountain to impressive heights, cause tidal waves that demolish coastlines, cause volcanoes to erupt, yet cannot influence solutes inside a tree or indeed a human? Bullshit!

lol
 

Offline Andrew K Fletcher

  • Neilep Level Member
  • ******
  • Posts: 2331
  • KIS Keep It Simple
    • View Profile
How do Trees Really lift Water to their Leaves?
« Reply #384 on: 15/11/2009 09:54:11 »
And all of you know what gravity is?

Please let me know at your earliest convenience as this problem has eluded the greatest minds and to this day still does!

 

Offline _Stefan_

  • Hero Member
  • *****
  • Posts: 814
    • View Profile
    • My Photobucket Album
How do Trees Really lift Water to their Leaves?
« Reply #385 on: 15/11/2009 10:07:26 »
Are you saying that you know better than the rest of us what gravity is and how it does and does not work?
 

Offline Andrew K Fletcher

  • Neilep Level Member
  • ******
  • Posts: 2331
  • KIS Keep It Simple
    • View Profile
How do Trees Really lift Water to their Leaves?
« Reply #386 on: 15/11/2009 10:25:09 »
The plates on the following paper show clearly the size of xylem and number of xylem in comparison to phloem. Tiny amount of return flow in the phloem = solvent dragging on all of the more dilute sap in the xylem, evaporation at the leaves reduces the volume of sap but increases the density of the sap and the denser sap moves down the tiny by comparison phloem vessels.

Experiments with different diameter tubes has shown this to be worth considering.

Using an inverted U tube with 3 tubes one of which contained a small amount of coloured salt solution added at the upper part where the tubes were joined with a T junction, the salt solution moved down as expected and the salt free water in the other two tubes moved up, caused by solvent dragging on all of the water molecules.

In the case of the tree, the narrowing of the xylem vessels in the canopy compared to the xylem vessels in the trunk and branches affords a method of extruding the large volume of water shedding off the majority to evaporation and returning the solutes down the phloem vessels.

The paper also relates to the problem with addressing constant cavitations known to take place and also known to refill and repair the cavitations. The cohesion tension theory relies on root pressure for this, yet the rattan does not exhibit root pressure.

http://www.amjbot.org/cgi/reprint/89/2/196.pdf
American Journal of Botany 89(2): 196–202. 2002.
XYLEM OF RATTANS: VESSEL DIMENSIONS IN
CLIMBING PALMS1
JACK B. FISHER,2,3,5 HUGH T. W. TAN,4 AND LESLIE P. L. TOH4
environmental factors. During periods of limited rainfall, rattans
and other lianas can experience severe water stress. At
such times, both stomatal closure and stem water storage
would aid survival. In other lianas, water-storing tubers or succulence
of stems and leaves are common (Fisher and Ewers,
1991). Rattans lack tuberous roots and their narrow stems have
a small proportion of parenchyma that could function in water
storage. However, their long stems with a relatively large volume
of water in wide vessels represent a significant water reservoir
that would become available if cavitation of vessels
occurred during periods of extreme water stress (Holbrook,
1995). If cavitation of wide vessels does play a role in water
supply during draught periods, then the question of vessel refilling
must be addressed. Further studies should also focus on
the water capacity of rattan stems compared to nearby nonclimbing
palms, as well as their relative degrees of stomatal
control.
At present, we have no information on production of embolisms
in rattan xylem. Yet the low percentage of nonfunctional
vascular bundles in old stems suggests either a lack of
vessel cavitation or a mechanism for refilling vessels (and tracheids).
Other lianas have root pressure that is sufficient to
refill air-filled xylem, as in Vitis (Sperry et al., 1987), or to
decrease xylem tension and thus assist in removal of embolisms
(Fisher et al., 1997). In a nonclimbing palm, Sperry
(1986) found that embolisms were dissolved when xylem pressure
potential approached that of the atmosphere during periods
of rain. When stem bases of cultivated species of Calamus,
Daemonorops, and Desmoncus (a climbing nonrattan palm)
were cut at dawn during rainy periods, no exudation appeared,
thus indicating no root pressure (Fisher et al., 1997); however,
there was an indication of root pressure in one species of Calamus
cultivated in a mountainous rainforest. We suggest that
future measurements for possible root pressure are needed to
better understand water conduction for rattans growing in natural
environments.


environmental factors. During periods of limited rainfall, rattans
and other lianas can experience severe water stress. At
such times, both stomatal closure and stem water storage
would aid survival. In other lianas, water-storing tubers or succulence
of stems and leaves are common (Fisher and Ewers,
1991). Rattans lack tuberous roots and their narrow stems have
a small proportion of parenchyma that could function in water
storage. However, their long stems with a relatively large volume
of water in wide vessels represent a significant water reservoir
that would become available if cavitation of vessels
occurred during periods of extreme water stress (Holbrook,
1995). If cavitation of wide vessels does play a role in water
supply during draught periods, then the question of vessel refilling
must be addressed. Further studies should also focus on
the water capacity of rattan stems compared to nearby nonclimbing
palms, as well as their relative degrees of stomatal
control.
At present, we have no information on production of embolisms
in rattan xylem. Yet the low percentage of nonfunctional
vascular bundles in old stems suggests either a lack of
vessel cavitation or a mechanism for refilling vessels (and tracheids).
Other lianas have root pressure that is sufficient to
refill air-filled xylem, as in Vitis (Sperry et al., 1987), or to
decrease xylem tension and thus assist in removal of embolisms
(Fisher et al., 1997). In a nonclimbing palm, Sperry
(1986) found that embolisms were dissolved when xylem pressure
potential approached that of the atmosphere during periods
of rain. When stem bases of cultivated species of Calamus,
Daemonorops, and Desmoncus (a climbing nonrattan palm)
were cut at dawn during rainy periods, no exudation appeared,
thus indicating no root pressure (Fisher et al., 1997); however,
there was an indication of root pressure in one species of Calamus
cultivated in a mountainous rainforest. We suggest that
future measurements for possible root pressure are needed to
better understand water conduction for rattans growing in natural
environments.
« Last Edit: 15/11/2009 10:49:03 by Andrew K Fletcher »
 

Offline Bored chemist

  • Neilep Level Member
  • ******
  • Posts: 8665
  • Thanked: 42 times
    • View Profile
How do Trees Really lift Water to their Leaves?
« Reply #387 on: 15/11/2009 10:48:48 »
And all of you know what gravity is?

Please let me know at your earliest convenience as this problem has eluded the greatest minds and to this day still does!


No, but I do know some of it's properties.
For exaple;
It is the force that holds me down on the planet.
It isn't responsible for the heat from the sun
It doesn't push water up trees.
It doesn't drive all life on earth.

The world's great scientists mighht not understand it fully but, unlike you, they know what not to atribute to it.
Why dd you post that rubbish?
 

Offline Andrew K Fletcher

  • Neilep Level Member
  • ******
  • Posts: 2331
  • KIS Keep It Simple
    • View Profile
How do Trees Really lift Water to their Leaves?
« Reply #388 on: 15/11/2009 10:52:02 »
Gravity is what drives the sun! therefore gravity is responsible for the heat from the sun. No gravity = no sun No gravity = no BC and no earth to stand on! No gravity = nothing
 

Offline Madidus_Scientia

  • Neilep Level Member
  • ******
  • Posts: 1451
    • View Profile
How do Trees Really lift Water to their Leaves?
« Reply #389 on: 15/11/2009 11:57:20 »
Gravity is a force, not energy.
 

Offline rosy

  • Neilep Level Member
  • ******
  • Posts: 1018
  • Chemistry
    • View Profile
How do Trees Really lift Water to their Leaves?
« Reply #390 on: 15/11/2009 13:09:37 »
Hehe.

Ok, now I'm laughing. We're in real making-stuff-up territory now.

Sure the sun wouldn't be able to exist without gravity, because the matter wouldn't be concentrated in one place... but to say that gravity drives the sun is just ludicrous. What "drives" the sun (in the sense of providing the actual energy) is nuclear fusion. Nuclear fusion is not, repeat not, driven by gravity.
« Last Edit: 15/11/2009 16:19:26 by rosy »
 

Offline Bored chemist

  • Neilep Level Member
  • ******
  • Posts: 8665
  • Thanked: 42 times
    • View Profile
How do Trees Really lift Water to their Leaves?
« Reply #391 on: 15/11/2009 14:22:18 »
"Gravity is what drives the sun!"
Still just plain wrong.
It's still time for you to learn some physics and maths.
Why did you post that rubbish?
Why don't you listen?
 

Offline Andrew K Fletcher

  • Neilep Level Member
  • ******
  • Posts: 2331
  • KIS Keep It Simple
    • View Profile
How do Trees Really lift Water to their Leaves?
« Reply #392 on: 18/11/2009 19:28:19 »
Hehe.

Ok, now I'm laughing. We're in real making-stuff-up territory now.

Sure the sun wouldn't be able to exist without gravity, because the matter wouldn't be concentrated in one place... but to say that gravity drives the sun is just ludicrous. What "drives" the sun (in the sense of providing the actual energy) is nuclear fusion. Nuclear fusion is not, repeat not, driven by gravity.
Where does the immense pressure come from that forces the atoms together to create fusion?
 

Offline Bored chemist

  • Neilep Level Member
  • ******
  • Posts: 8665
  • Thanked: 42 times
    • View Profile
How do Trees Really lift Water to their Leaves?
« Reply #393 on: 18/11/2009 20:45:47 »
Who cares?
If it were not for fusion all you would get was squashed gas.

Saying the sun is driven by gravity is like saying my central heating runs on a match.
OK, without a match to light the pilot light, the heating wouldn't work.
But it's still gas that heats my house.

It's still time for you to learn some physics and maths.
Why did you post that rubbish?
Why don't you listen?
 

 

Offline Madidus_Scientia

  • Neilep Level Member
  • ******
  • Posts: 1451
    • View Profile
How do Trees Really lift Water to their Leaves?
« Reply #394 on: 11/12/2009 19:47:27 »
I don't think you understand the gravity of the situation
 

Offline Andrew K Fletcher

  • Neilep Level Member
  • ******
  • Posts: 2331
  • KIS Keep It Simple
    • View Profile
How do Trees Really lift Water to their Leaves?
« Reply #395 on: 21/03/2010 10:03:04 »
Titre du document / Document title
Osmosis and solute-solvent drag : Fluid transport and fluid exchange in animals and plants
Auteur(s) / Author(s)
HAMMEL H. T. ; SCHLEGEL Whitney M. ;
Résumé / Abstract
In 1903, George Hulett explained how solute alters water in an aqueous solution to lower the vapor pressure of its water. Hulett also explained how the same altered water causes osmosis and osmotic pressure when the solution is separated from liquid water by a membrane permeable to the water only. Hulett recognized that the solute molecules diffuse toward all boundaries of the solution containing the solute. Solute diffusion is stopped at all boundaries, at an open-unopposed surface of the solution, at a semipermeable membrane, at a container wall, or at the boundary of a solid or gaseous inclusion surrounded by solution but not dissolved in it. At each boundary of the solution, the solute molecules are reflected, they change momentum, and the change of momentum of all reflected molecules is a pressure, a solute pressure (i.e., a force on a unit area of reflecting boundary). When a boundary of the solution is open and unopposed, the solute pressure alters the internal tension in the force bonding the water in its liquid phase, namely, the hydrogen bond. All altered properties of the water in the solution are explained by the altered internal tension of the water in the solution. We acclaim Hulett's explanation of osmosis, osmotic pressure, and lowering of the vapor pressure of water in an aqueous solution. His explanation is self-evident. It is the necessary, sufficient, and inescapable explanation of all altered properties of the water in the solution relative to the same property of pure liquid water at the same externally applied pressure and the same temperature. We extend Hulett's explanation of osmosis to include the osmotic effects of solute diffusing through solvent and dragging on the solvent through which it diffuses. Therein lies the explanations of (1) the extravasation from and return of interstitial fluid to capillaries, (2) the return of luminal fluid in the proximal and distal convoluted tubules of a kidney nephron to their peritubular capillaries, (3) the return of interstitial fluid to the vasa recta, (4) return of aqueous humor to the episcleral veins, and (5) flow of phloem from source to sink in higher plants and many more examples of fluid transport and fluid exchange in animal and plant physiology. When a membrane is permeable to water only and when it separates differing aqueous solutions, the flow of water is from the solution with the lower osmotic pressure to the solution with the higher osmotic pressure. On the contrary, when no diffusion barrier separates differing parts of an aqueous solution, fluid may flow from the part with the higher osmotic pressure to the part with the lower osmotic pressure because the solute molecules diffuse toward their lower concentration and they drag on the water through which they diffuse. This latter osmotic effect (diffusing solute dragging on solvent or counterosmosis) between differing parts of a solution has long been neglected and ignored when explaining fluid fluxes in plant and animal physiology. For two solutions separated by a semipermeable membrane, osmosis is the flow of its solvent from the solution with the lower solute concentration into the solution with the higher solute concentration. For two contiguous solutions not separated by a semipermeable membrane, counterosmosis is the flow of solution with the higher solute concentration toward the solution with the lower solute concentration.
Revue / Journal Title
Cell biochemistry and biophysics   ISSN 1085-9195   CODEN CBBIFV 
 

Offline Bored chemist

  • Neilep Level Member
  • ******
  • Posts: 8665
  • Thanked: 42 times
    • View Profile
How do Trees Really lift Water to their Leaves?
« Reply #396 on: 21/03/2010 21:47:08 »
So?
 

Offline Andrew K Fletcher

  • Neilep Level Member
  • ******
  • Posts: 2331
  • KIS Keep It Simple
    • View Profile
How do Trees Really lift Water to their Leaves?
« Reply #397 on: 19/04/2010 17:54:23 »

Experiment showing solvent drag and solute density applied tension to water filled vertically suspended silicone tubing.

« Last Edit: 24/04/2010 09:49:38 by Andrew K Fletcher »
 

Offline Bored chemist

  • Neilep Level Member
  • ******
  • Posts: 8665
  • Thanked: 42 times
    • View Profile
How do Trees Really lift Water to their Leaves?
« Reply #398 on: 19/04/2010 18:19:58 »
The experiment shows that salt water is denser than fresh water.
This bloke
http://en.wikipedia.org/wiki/Samuel_Plimsoll
made use of the fact a while ago; but it wasn't exactly news then.

Incidentally, silicon is what chips are made from; silicone is used to make that sort of tubing and huge boobs.
The walls of that tubing are more or less elastic so it's a poor model for things like blood vessels which have muscular walls.

Essentially, as far as I can see, all you have done here is play with coloured water.
 

Offline Tritalon

  • First timers
  • *
  • Posts: 1
    • View Profile
How do Trees Really lift Water to their Leaves?
« Reply #399 on: 16/08/2010 21:00:32 »
Hello.

I have wondered what raises the water in plants. This video:
explains that driving force is transpiration, a process in which water diffuses from stomata into the atmosphere.

What exactly pulls the molecules of water into the air?
 

The Naked Scientists Forum

How do Trees Really lift Water to their Leaves?
« Reply #399 on: 16/08/2010 21:00:32 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums
 
Login
Login with username, password and session length