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HarveyWalbanger
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Explaining the physics of transpiration bags?
#15139025 - 09/26/11 09:05 PM (12 years, 7 months ago) |
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http://www.youtube.com/watch?v=vxB61tGEurw
I'm having trouble describing whats going on here. I've been tripping over the water-vapor equilibrium and dewpoints etc for about an hour now.
I've got faith that one of you guys can explain whats going on here rather easily.
Edited by HarveyWalbanger (09/26/11 09:07 PM)
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johnm214


Registered: 05/31/07
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Loc: Americas
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Re: Explaining the physics of transpiration bags? [Re: HarveyWalbanger]
#15139169 - 09/26/11 09:38 PM (12 years, 7 months ago) |
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I doubt its anything nearly that sophisticated.
My guess is that that water is merely the result of water vapor 'exhaled' out through the leaves.
The leaves of a plant have to respire to exchange gasses. Some water will be expelled in the process. Additionally, plants generally use capillary action for their main means of transporting chemicals about the plant, especially from the soil and roots to the leaves. In such a system, you need to remove the water at the top of the capillary to make room for the water coming up. The amount of water removed would be correlated with the amount of solvated chemicals transported up the plant form the roots.
When the plant is in the sun, the exchange of gasses and need for materials from the roots will likely be at its highest, so both the capillary system and respiration actions will be in full gear. The only thing the bad does, in my estimation, is prevent the water from escaping and providing a surface to condense on .
I'm not very knowledgeable about plant stuff, but that makes sense to me.
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HarveyWalbanger
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Re: Explaining the physics of transpiration bags? [Re: johnm214]
#15139251 - 09/26/11 09:56 PM (12 years, 7 months ago) |
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Yeah, but it leaves the plant as evaporated water vapor (I think) so theres some condensation mechanism at work...
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johnm214


Registered: 05/31/07
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Re: Explaining the physics of transpiration bags? [Re: johnm214]
#15139431 - 09/26/11 10:35 PM (12 years, 7 months ago) |
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Oh, sure, the water leaves the plant and enters the bag. As the bag is closed, it is a fixed volume. Being such, all the water enters the bag and stays there. As the water vapor concentration increases eventually it pushes the relative humidity past 100% and the excess water condenses.
The bag simply reduces the volume of atmosphere you need to saturate with gaseous water. As the plant has a limited volume of water to ouput, this increases the quantity of water your able to obtain and shortens the time it takes to collect a given amount of water.
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HarveyWalbanger
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Re: Explaining the physics of transpiration bags? [Re: johnm214]
#15139647 - 09/26/11 11:23 PM (12 years, 7 months ago) |
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Exactly the answer I was lookin for. Thank ya much.
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ChuangTzu
starvingphysicist



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Re: Explaining the physics of transpiration bags? [Re: johnm214]
#15144359 - 09/27/11 09:38 PM (12 years, 7 months ago) |
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Quote:
johnm214 said: Oh, sure, the water leaves the plant and enters the bag. As the bag is closed, it is a fixed volume. Being such, all the water enters the bag and stays there. As the water vapor concentration increases eventually it pushes the relative humidity past 100% and the excess water condenses.
It probably also requires a temperature drop unless the stomata have some kind of active pumping mechanism, which I'm pretty sure they don't... Otherwise the relative humidity won't breach 100% in the first place.
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5HTSynaptrip
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Re: Explaining the physics of transpiration bags? [Re: ChuangTzu]
#15146232 - 09/28/11 09:18 AM (12 years, 7 months ago) |
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There are proton pumps that trigger a cascade of different ions to change gradients, which ultimately leads to turgidity and opening of the stoma. Enclosing a portion of the plant raises the humidity and helps the opening of the stomata in an otherwise dry climate.
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Science is a way of thinking much more than it is a body of knowledge. - My hero, who will be forever remembered, Carl Sagan.
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