Placeholder Image

Subtitles section Play video

  • in a previous video, I showed you that you can on Lee suck up a straw that's 10.3 meters long, and that's even if you can create a perfect vacuum inside your mouth.

  • If you haven't seen the original video, check it out.

  • But that raises an interesting question.

  • Which is?

  • How can these trees, which are 100 meters high, get the water all the way from their roots up to the leaves?

  • The argument is you're alluding to is that if you're sucking water up through a drinking straw, for example, you can only have a stroll 33 feet long.

  • The reason for this height limit is because the weight of the water in a column must be supported by the pressure difference between the top and the bottom.

  • So the bottom you're gonna have atmospheric pressure and the lowest pressure you can produce the top would be a vacuum.

  • That is zero pressure so atmospheric pressure can support a column of water that is only 10 meters high.

  • What's worse is if you were able to create a vacuum, the water would start boiling spontaneously.

  • That's called capitation, and obviously that can't be taking place within a tree.

  • So how are they doing it?

  • Well, we started to develop some different theories.

  • My guess.

  • Those people talk about this being continuous water column and what they when When you say that you think is big, like empty pipe, right?

  • That's what we're picturing.

  • But I think what's more likely to be the truth?

  • This big tube, which you're saying needs to be filled with water, is actually made up of cells.

  • The tree effectively has valves in it, so you don't have a column of water that is much higher than 33 Beatles, less so that the water is pumped up by osmotic pressure due to differences in concentration of sugars and so on.

  • But each individual stage, it's just quite a small one.

  • My guess is that it's probably more like a bucket brigade where once you know, here, right and there's sunlight coming in and and he took the water in, the water, evaporates into the water, goes off his water vapor, rises up with these guys like my bucket's empty.

  • I want some more water, and this is a self so here, but this one can give the water there because locally, like surrounded by water, it's a little bit of water will go there by osmotic pressure.

  • Now, another theory is that osmotic pressure at the base could actually push the water all the way up the tree.

  • If the sol you concentration is different enough between the roots and the water in the surrounding soil, then water would actually want to push into the roots in order to equalize the solid concentrations.

  • That could create a positive pressure, which would push the water up the tree.

  • And this hypothesis led me to being challenged to blow water up a tube.

  • Now the water, as you can see, is very Tasci in color.

  • Three, 21 go.

  • Yeah, I know now my ability to blow water up that tube was impressive, but I don't really think that a tree would be able to get so much osmotic pressure at the roots that it could push the water up 100 meters.

  • Well, some people may be wondering why we haven't talked about capillary action yet.

  • That's due to the adhesion between the water molecules and the walls of the tube so you can suck water up through ah perforated materials.

  • Now, I'm not sure that the tubes inside a tree are small enough for this effect to have a significant impact.

  • But it may.

  • Well, I don't want to give you the complete answer yet.

  • I'd like you guys to tell me what you think and maybe post a video response.

  • I'll tell you that I had a significant misconception that was stopping me from working this out.

  • So if you can spot with that is I do let me know.

  • And let me give you a summary of the ideas we came up with.

  • One that the tree does not contain a continuous water column.

  • Number two osmotic pressure at the roots may be pushing the water up the tree number three Osmotic pressure throughout the tree helps pull the water up and number four capillary action.

  • So let me know what roles you think those different factors play in allowing a treated.

in a previous video, I showed you that you can on Lee suck up a straw that's 10.3 meters long, and that's even if you can create a perfect vacuum inside your mouth.

Subtitles and vocabulary

Operation of videos Adjust the video here to display the subtitles

B1 INT water pressure tree column tube capillary

How Can Trees Be Taller Than 10m?

  • 0 0
    林宜悉 posted on 2020/03/28
Video vocabulary