Transpiration - help

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Crux
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Transpiration - help

Post by Crux » Thu Nov 10, 2005 6:37 pm

Okay, i'm a little confused about a certain aspect in transpiration.

I know that:
- plants have a layer of waxy cuticle to prevent water-loss
- transpiration is dependent on the humidity/weather, and the moisture in the soil, as well internal factors: i.e. photosynthesis (for the CO2).

But, does gas exchange occur across a dry or moist membrane? and why? Plants cool themselves when they transpire, but the membrane wouldn't be moist... would it?

I'm kind of stranded with this one, although i'm leaning more to "dry membrane". Your help would be greatly appreciated. :D

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canalon
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Post by canalon » Thu Nov 10, 2005 10:36 pm

The cuticule at the surface of the leaves blocks the transpiration, but this cuticule is not continuous, it is full of small holes (stomates in french) that allow both gaseous exchanges (for respiration and photosynthesis) and perspiration.
So perspiarion rate vary with the opening of the stomates and the surface of the leaves is not moist.

Is that what you are asking/
Patrick

Science has proof without any certainty. Creationists have certainty without
any proof. (Ashley Montague)

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mith
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Post by mith » Thu Nov 10, 2005 11:47 pm

it actually needs to be wet because the water allows the gases to dissolve in it.
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Accepting hardships as the pathway to peace;
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Post by Crux » Fri Nov 11, 2005 5:17 pm

hmmm... but you get the water from the vascular veins.

Could it be that the water diffuses along the cuticle and dissipate into the atmosphere... thus actually making the sufface moist?

OR

It could evaporate as soon as it leaves the stoma?

---help :(

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mith
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Post by mith » Fri Nov 11, 2005 10:17 pm

The membrane and the cuticle are different things, the cuticle is a waterproof layer, very little watter goes out that way.
Living one day at a time;
Enjoying one moment at a time;
Accepting hardships as the pathway to peace;
~Niebuhr

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Post by Crux » Sat Nov 12, 2005 7:32 pm

I know.. ahhh!!! this driving me nuts.

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