0 Members and 1 Guest are viewing this topic.
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.
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.
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.
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.
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.
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
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.
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 !!!!!
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.
quote:Yes even if its on top of something else! Take a look at the flow of dense rock pulled towards the Earths core
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!!!!
quote:And for every action there must be a reaction !!!!!
quote:"The explanation requiring the fewest assumptions is most likely to be correct."
quote:Originally posted by rosyIf 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.
quote: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.
quote:Loss of water from the leaves results in water being drawn up from the roots via the xylae(osmosis).
quote: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
quote:, 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.
quote: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[/quote]Ok I will concede that it may not be true amber in the sense of fossilized resin, but the stuff did come from a tree all said and done [:I]Andrew"The explanation requiring the fewest assumptions is most likely to be correct."K.I.S. "Keep it simple!"
quote:Absolute nonsense, osmosis requires the belief that water can attract water up a tree and out through the leaves? I cannot see any logic in your argument here.
quote:Firstly, it is not a convection system. It is a flow and return system which operates when concentrations of denser solutes occur above less dense solutes due to evaporation.
quote:In the spring, there is an initial temperature change, which initiates the flow and return system, causing the circulation inside the leafless tree to flow, and to generate both positive and negative pressures within the moving fluids as it goes.
quote:Actually there is a very good reason for more water to follow, that being the cohesiveness of water molecules adhering to water molecules. This is precisely why I keep asking you to repeat the experiments.
quote:Sorry, I disagree with you, the weight of the water in the opposing side is irrelevant
quote:The coloured solution will flow in the opposite side to the siphon, and can be clearly seen in the turbulence of the coloured solution as it interacts with the clean solution.
quote:But somewhere within the plant or tree, there is a pathway for gravity to draw solutes down
quote:This flow system will always run in the path of least resistance, be it horizontal, down or up, it makes no difference. But somewhere within the plant or tree, there is a pathway for gravity to draw solutes down,
quote:Originally posted by daveshortsquote:Absolute nonsense, osmosis requires the belief that water can attract water up a tree and out through the leaves? I cannot see any logic in your argument here.You may find this stuff interesting about osmosishttp://www.chaosscience.org.uk/pub/public_html//article.php?story=20050301222247333and http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/ospcal.htmlhas a nice program for calculating osmotic pressuresIf evaporation keeps the concentration of the liquids in teh leaf hight, osmosis can generate the appropriate pressures to suck water out of the xylem, and the column of water in the xylem behaves like a wire (because it is cohesive) so if you pull at the top the whole column moves up, it all sounds consitent to me...
_____ <- membrane | | | | | | | | <- code | | |__| |__| | | | | <-resivoir |_________|
quote:Originally posted by daveshortsin the diagram where i wrote code I meant tube... I think I need to eat supper