I have a bit of homework for you guys... don't be intimidated by the size of my post- I'm not asking you to do it, I just want a little direction and clarification.

I have a lab write-up due in High School Biology tommorow, but I am really confused about it. I was wondering if anybody could point me in the right direction here.

Experiment
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We did this experiment in class.

There are 3 plants. One is static, one is being fanned with wind, and one is inside a bag to increase humidity. We measured the water intake of each plant every 2 minutes, in inches. Here is the data:

As you can see fanning the plant increases it's intake of water and the bag (humidity) decreases it's intake. I will later post a graph (which is required of me anyway)

So I am supposed to interperate this data and draw conclusions related to our current unit. This is where I am confused. What does this have to do with transperation, osmosis, root pressure, and transpiration tension?

Here is the format of the lab:


Again, please don't try and do this... I just need some clarification to what the experiment has to do with Osmosis, Root Pressure, and Transpiration Tension.

Thanks...

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[This message has been edited by Mystic0 (edited June 03, 2004).]

Do your own homework. (PS: I don't understand any of this and I looked at it for a good 5 minutes.)

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<Outlaw_Torn> you mean your related to that damned sasquatch, Mech?
<MechWarrior> Lets just say the part of the family tree that does fork has bossy the goat in it.

<ubuu> does hitler have a last name?

[This message has been edited by MechWarrior (edited June 03, 2004).]

Here is a graph.
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Blue is static (control)
Pink is fanned
Yello is bagged (humid)


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When a man and a woman love eachother very much

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Dude I've seen girls and I've seen lobsters, and that is totally a lobster.

-Correction

Wha...?

Wrong thread?

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I think I am understanding this, I just need to read about transperation.

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*tries to remember Yr12 biol*

When a plant transpires, water is lost through pores on the leaves. The amount of water that is lost is related to the vapour pressure of water in the atmosphere. The higher the water vapour pressure (high humidity), the less of a concentration gradient there is for the plant to lose water, hence, more water stays in the plant and less is lost.

With fanning, the opposite happens. The air moves water vapour away from the plant and any water on the pores of the leaves, this increases the concentration gradient and causes more water to move up through the plant.

So high humidity (the bag) decreases transpiration due to a higher water pressure in the air, while low humidity (the fan) increases transpiration for the opposite reason.
With high transpiration, osmosis at the roots is increased in order to replace the fluid that is lost to the atmosphere.

Root pressure refers to the amount of solute in the roots. The solute concentration in the plant is higher than in the soil due to active transport of nutrients in. This sets up a concentration gradient and increases the amount of water drawn into the plant (increased osmosis).

I’m not 100% sure but I think that transpiration tension refers to “transpiration pull”. The column of sap/water moves up through the plant because of transpiration, but the reason the column of fluid sticks together is due to the surface tension of the fluid. The concentration gradient at the leaves causes water to be drawn up from the roots and due to the surface tension of water molecules, the leading bit of water “pulls” up the molecules behind it.

So low humidity results in increased transpiration, which isn’t all that flash for the plant. As a result water in the plant decreases which increases the solute concentration (increased root pressure). The increased root pressure draws in more water via osmosis to compensate for the loss of water through transpiration. Don’t know how the transpirational tension fits in though. Yr 12 biol was a loooong time ago. High humidity would be the opposite.

Hope this helps.


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This one day I went to change my password, but being the clever chappy that I am, I accidently typed the new pw into the e-mail address bar and clicked submit, hence the slightly modified new user name. Go me and my awesome computer skills.

Thank you very much, this helps alot.

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Okey, printed the report off and going to school.

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