There are stories that the moss on trees in temperate rainforests allow the tree to pull water from their branches instead of the ground, increasing their max height.
For a while there were people poaching the moss that facilitated this, which is a problem because it grows only inches per year.
Not that it really matters, but the article also refers to it as “drawing water to the top”. That seems more representative of reality than “pumping water from the bottom”.
If you think of it that way, you have a real problem. It only takes about 10 meters for the weight of a column of water to create enough downward force that it starts vaporizing, at which point no pumping action works. This is why any deep well has a submerged pump. You simply can't pull water upward further than that with negative pressure in the Earth's atmosphere. It must be pushed with positive pressure instead.
This is why the question is interesting. You can't just suck water to the top of a 60 meter tree. There must be some kind of positive-pressure pumping involved.
The trick for trees is capillaries, which change the equation. The 10 meter limit only applies to larger columns. With capillaries there's a high negative tension that allows evaporation from leaves to pull the xylem sap up 100 meters or more.
There's no free lunch here. The Sun drives the evaporation, and if the tree were in a closed system with no solar input, the humidity would eventually get high enough to stop it.
One of the things Susan Simard proved was that deep rooted trees that had found subterranean water continue pulling that water at full speed at night when transpiration is low, and that water finds its way into the fungal networks in the soil and into nearby plants.
Simard attributes intention to this, but osmosis is “fair”. It seeks to move water to where sugars are and sugars to where water is. So a plant giving up sugars will receive water, and one low on water will give up sugars in the process of equalization.
Do fungi contain pumps to maintain disequilibrium in this work? I could not say. But even when they first learned the trick of tapping roots the basic premise would have worked in a rudimentary fashion woth no further optimization.
the research is relevant to the issue of transpiration column hieght as a postulated limitation to overall hieght of any tree.
a column of water is pulled by hydrogen bonding between molecules in a tug of war fashion, the top of the column is where water is dissociated from the column at such a rate as to maintain low pressure with respect to the column[xylem]
in summary water moves from bottom to top in a transpiration stream, that ultimately ejects water vapour from the leaves, resulting in a low efficiency mechanism, that loses a lot of the water but occurs at such a rate that the low efficiency is "good enough" for whats needed.
Maybe it's not more trouble pumping, eh, sucking water up. But that the top branches are the last ones to get water in periods of draught, and have therefore more resilience?
This goes against all previous research/measurements for actually tall trees (looks like they only considered up to 80m) and the fact that there are exactly zeros trees in the world taller than 130 meters [1]. Wide capillaries at the base, like stated in the article, don't seem to be related.
There’s also a theory that the moss on these trees is mutualism instead of simply epiphytic. The moss holds moisture, which can be accessed by the tree.
Similarly, it blows my mind that all trees are made of air, specifically the carbon in it. I used to think that the biomass must come from the soil, but reality is more interesting.
Too bad we cut it down, along with almost every other giant Douglas-fir.
For a while there were people poaching the moss that facilitated this, which is a problem because it grows only inches per year.
Hm, may be because they are not really "pumping" the water?
This is why the question is interesting. You can't just suck water to the top of a 60 meter tree. There must be some kind of positive-pressure pumping involved.
There's no free lunch here. The Sun drives the evaporation, and if the tree were in a closed system with no solar input, the humidity would eventually get high enough to stop it.
Simard attributes intention to this, but osmosis is “fair”. It seeks to move water to where sugars are and sugars to where water is. So a plant giving up sugars will receive water, and one low on water will give up sugars in the process of equalization.
Do fungi contain pumps to maintain disequilibrium in this work? I could not say. But even when they first learned the trick of tapping roots the basic premise would have worked in a rudimentary fashion woth no further optimization.
... that would be the least of the tree's problems.
Or the high pressure is down here, whichever way you want to look at it.
https://en.wikipedia.org/wiki/Xylem#Cohesion-tension_theory
a column of water is pulled by hydrogen bonding between molecules in a tug of war fashion, the top of the column is where water is dissociated from the column at such a rate as to maintain low pressure with respect to the column[xylem]
in summary water moves from bottom to top in a transpiration stream, that ultimately ejects water vapour from the leaves, resulting in a low efficiency mechanism, that loses a lot of the water but occurs at such a rate that the low efficiency is "good enough" for whats needed.
So sucking / pulling?
> leaves which have adapted to withstand greater water stress before wilting.
That must be one of the "adjustments to water transport" mentioned. So I suggest that they do, in fact, have trouble pumping water to top branches.
[1] https://www.sfgate.com/science/article/REDWOODS-How-tall-can...
Coalescence of coastal fog accounts for a considerable part of the trees' water needs.[23]
https://en.wikipedia.org/wiki/Sequoia_sempervirens#Fog_and_f...
https://en.wikipedia.org/wiki/Sequoia_sempervirens
[1] https://www.sfgate.com/science/article/REDWOODS-How-tall-can...