Globule c doth hitt away the particle b

February 5, 2015 4:11 PM

According to the laws of Newtonian physics, capillary action occurring in Earth's atmosphere should be able to lift water 10 meters high at most. For centuries scientists struggled to ascertain how, then, trees were able to lift water considerably higher. Finally, in 1894, Irish plant physiologists H. H. Dixon and J. Joly proposed the cohesion-tension theory which remains the leading theory today, though it is still not fully understood (PDF).

On the topic of Newton and his physics, a recently unearthed note from Isaac Newton's college days shows that he had it figured out 200 years before anybody else.

(Previously).
posted by Hot Pastrami! (15 comments total)

Huh. I'm not sure I believe that trees don't generate pressure in the root system rather than relying entirely on wicking.
posted by Tell Me No Lies at 5:22 PM on February 5, 2015

This reminds me of Fermat's fabled Elegant Proof Too Big For The Margin that drove mathematicians doo-lally bonkers for eons. They eventually (VERY eventually) figured it out with Crazy Future Math, but we'll never know if Fermat (A) actually discovered a proof that used the math available to him at the time, (B) had a proof that wasn't actually correct or (C) was lying to (C1) encourage the community to find a proof, (C2) make himself look awesome or (C3) troll us all.
posted by BiggerJ at 5:30 PM on February 5, 2015 [4 favorites]

we'll never know if Fermat (A) actually discovered a proof that used the math available to him at the time

I think at this point that can be fairly safely ruled out.
posted by yoink at 5:49 PM on February 5, 2015

Veritasium explains.
posted by delicious-luncheon at 5:59 PM on February 5, 2015 [3 favorites]

I still like to think Fermat *might* have come up with something really elegant (too big to fit in the margins but less than 200 pages or whatever the current solution is), although it's more likely he just thought he did.
But this is a pretty brilliant conjecture on Newton's part. No slouch he.
posted by uosuaq at 6:12 PM on February 5, 2015 [1 favorite]

Huh. I'm not sure I believe that trees don't generate pressure in the root system rather than relying entirely on wicking.
posted by Tell Me No Lies

Luckily, this is exceedingly easy to experimentally validate. Drill a hole at the very base of a tree, and thread a pressure gauge into it. If anyone asks, tell them that you're checking up on your clockwork orange grove.
posted by TheNewWazoo at 8:06 PM on February 5, 2015

he had it figured out 200 years before anybody else

Newton was such a hipster.
posted by 1adam12 at 8:51 PM on February 5, 2015 [2 favorites]

I've had a 900+ page biography of Newton sitting on my bookshelf unread for at least 15 years. It is giving my the evil eye right now.
posted by neuron at 10:21 PM on February 5, 2015 [1 favorite]

Huh. I'm not sure I believe that trees don't generate pressure in the root system rather than relying entirely on wicking.

Excerpt from the 5th link:

Roots are not needed. This was demonstrated over a century ago by a German botanist who sawed down a 70-ft (21 meters) oak tree and placed the base of the trunk in a barrel of picric acid solution. The solution was drawn up the trunk, killing nearby tissues as it went.
posted by Hot Pastrami! at 10:31 PM on February 5, 2015 [1 favorite]

(D) Fermat used the meth available to him at the time
posted by iotic at 11:40 PM on February 5, 2015 [1 favorite]

Roots are not needed. This was demonstrated over a century ago by a German botanist who sawed down a 70-ft (21 meters) oak tree and placed the base of the trunk in a barrel of picric acid solution. The solution was drawn up the trunk, killing nearby tissues as it went.

That only proves that wicking is present, not that pressure is absent...
posted by Tell Me No Lies at 2:03 AM on February 6, 2015

From the very ond of the linked article on the cohesion-tension theory:
"[A]lthough root pressure may play a significant role in water transport in certain species (e.g., the coconut palm) or at certain times, most plants meet their needs by transpiration-pull. "
posted by hat_eater at 4:22 AM on February 6, 2015

Newton was such a hipster.

*singsong* I smell a meeeeeeme
posted by echocollate at 5:05 AM on February 6, 2015 [1 favorite]

That only proves that wicking is present, not that pressure is absent...

If you've ever watched a tree being cut down, while there can be some liquid right at the cut surface, water doesn't gush forth like it would if there was pressure behind it.
posted by sneebler at 8:19 AM on February 6, 2015 [2 favorites]

It had been my understanding that it's a siphon, not a pump. At the top of a tree, even without leaves, there's a whole bunch of evaporative surface hanging out in the breeze. At the bottom there's a whole bunch of absorptive surface hanging out underground with water, which is drawn up through a combination of capillary action and suction from evaporating or otherwise used up water at the top. If you cut down a tree, nothing gushes out because there's neither capillary action nor suction drawing it upward any more.

I'm neither and expert nor am I particularly invested in this explanation.
posted by cmoj at 9:04 AM on February 6, 2015