111–120 of 134 posts
plants are very brave, both metaphorically and physically.
Earlier quoted context omitted.
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 transpirat…
> a transpiration stream, that ultimately ejects water vapour from the leaves I don't believe this is correct, or rather is not a required component of the system but rather incidental. The chemical system within the leaf removes water via chemical reaction. There is a respiration process to dispose of waste gasses. Water vapor happens to be lost to this process not of necessity but rather because keeping it separate…
No they have different strategies to minimize water loss that comes with exhanging CO2 & O2 to the atmosphere. For example:
https://en.wikipedia.org/wiki/Crassulacean_acid_metabolism
Portulacaria Afra (elephant bush) is a nice example. It can switch between C3 and CAM photosynthesis pathways as needed.
The largest tree on record is rejected in part because it's over the theoretical limit: https://en.wikipedia.org/wiki/Nooksack_Giant Too bad we cut it down, along with almost every other giant Douglas-fir.
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.
I grow marijuana and chillies from time to time. I got good at it. I will say that plants are malleable in untold ways and so I find this article to be unsurprising. Plants will do what they need to do in the end. I've done stuff like co2 bombing, and increasing nutrients to the point to where I get a whole new ecosystem of insects and an entirely new situation. It is such fascinating stuff that it's actually the lif…
There is apparently such a thing as "Computational Botany", where you model virtual plants.
> These vessels have evolved intricate adaptations that can maintain the water in liquid form, even under the extreme low pressures This sentence undersells the phenomenon quite a bit: the “extreme low pressure” is in fact several bars of negative pressure and the challenge of maintaining water in liquid form is avoiding cavitation . I was exposed to the physics of trees though the entrance exam to École Polytechniqu…
See also Veritasium on that topic:
A bucket brigade works just as well up ten flights of stairs as up one hundred. So does a system of opening and closing valves.
We can pump water from a bucket on one floor of building to a bucket on the next floor easily. Then we can repeat the same thing at the next floor; the pressure from the numerous floors above doesn't factor in because there isn't a connected water column.
Earlier quoted context omitted.
more like capillary action. https://en.wikipedia.org/wiki/Xylem#Cohesion-tension_theory
Capillary action is subject to the same limits as suction at the top. Capillary action can't increase the water pressure at the bottom of the tree. If you put a straight thin capillary tube upright in water so it sucks up water from the bottom, no matter how thin, it can't draw water up above ~10m of water level.
xylem is not a straw, is no where near the diameter of a straw, and its[transpiration] is not about increased pressure its about decrease.
psi values at the apical mesenchyme are around -100 to -150 megapascals dependent on species and relative humidity at the stoma.
physics and biology although intertrined are not the same catechisms, heres a link toward most of m.j. canny's work.
https://www.researchgate.net/scientific-contributions/M-J-Ca...
here is is a basic scheme of things
Water Movement in Xylem:
https://oercommons.org/courseware/lesson/87595/student-old/?...
Xylem:
https://en.wikipedia.org/wiki/Xylem
Hydrogen bond:
Kurzgesagt has two videos on trees addressing this and other questions. https://m.youtube.com/watch?v=ZSch_NgZpQs https://m.youtube.com/watch?v=pHJIhxZEoxg
Earlier quoted context omitted.
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.
And leaves can absorb moisture from water droplets on their leaves. Like from rain or foggy sea winds. Why go through a transport system when the water is right where it's needed?
Water and solute movement in plants:
https://www.ebsco.com/research-starters/anatomy-and-physiolo...
there is a disconnect between the roots and the xylem, its not a throughway, there is a switchover.
Plant Roots and Mineral Nutrition: An Overview of Molecular Basis of Uptake and Regulation, and Strategies to Improve Nutrient Use Efficiency (NUE)
https://link.springer.com/chapter/10.1007/978-981-15-9380-2_...
Kurzgesagt has two videos on trees addressing this and other questions. https://m.youtube.com/watch?v=ZSch_NgZpQs https://m.youtube.com/watch?v=pHJIhxZEoxg
I'd be careful suggesting Kurzgesagt because they push propaganda for large corporations https://www.youtube.com/watch?v=HjHMoNGqQTI