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HELP NEEDED- PLANT TRANSPIRATION!

Discussion of the distribution and abundance of living organisms and how these properties are affected by interactions between the organisms and their environment

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HELP NEEDED- PLANT TRANSPIRATION!

Postby jeffress » Mon Aug 06, 2007 6:50 am

Hey just wondering if anyone who knows about plant transpiration would like to help me with a year 12 Biology assignment!

I did an experiment using plant cuttings in a beaker of water in different conditions such as light and dark and wind (in front of a floor fan) and no wind. According to research that ive done the plants in the light should of transpired and used more water than the ones in the dark, but results show that the cuttings in the dark transpired more.
The same with the wind, the fan should regulate the humidity around the cuttings making them transpire more but the ones not in the wind transpired more!

Can anyone explain this for me!!!
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Postby mith » Mon Aug 06, 2007 3:57 pm

Try repeating it. Maybe switch the plants around.
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Postby AstusAleator » Tue Aug 07, 2007 11:30 pm

Were all plant cuttings roughly the same mass and surface area?

Was the water level in each beaker equal?

Were temperature and humidity held constant over all samples?

What type of light was the light sample in?

Was the dark sample in complete darkness?

How are you getting your results? (ie are you looking at water level? or something else?)

How long are you conducting the study?

I agree with Mith that you should repeat the study. Pay attention to the details.
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PLANT TRANSPIRATION

Postby jeffress » Wed Aug 08, 2007 8:52 am

Well the thing is we did repeat the transpiration experiment and we got the same results.

The plants were practically all the same size with the same amount of foliage and all off the same plant.
The water in each beaker was all 100ml with 5ml of veg oil on top to stop evaporation.
The light sample was under a fluro light for 24hours a day for 3 days (i think it was too close to the light though and the stomata probably closed instead of opened).
The dark plants were keep in a sealed cupboard under a sink the whole time and each time we recorded results, the water level was recorded then the plants were put back to how they were.

The temperature was not taken though (which I am regreting) so Im not sure if it was constant the whole time so that might be the problem, but over those three days, to a person they didnt vary massively or anything so Im not sure whats up.

Help lol. Plants arent my forte! :roll:
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Postby mith » Wed Aug 08, 2007 5:07 pm

How much was the difference anyway? If all else fails I think you should redesign the experiment so that you're measuring transpiration(put bag over plants). Otherwise it seems you have a problem finding an evaporation leak...

*Note that with increased light, the plants might be using more water, but it might not have anything to do with transpiration.
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Postby AstusAleator » Thu Aug 09, 2007 4:10 pm

Jeff, if you don't mind, could you post your hypothesis and protocol?

You say your dark sample was in a sealed cupboard. Does that mean air-tight? If so, then your light-sample as well as your wind/nonwind samples should also have been in air-tight compartments. You need to keep as many variables as possible constant between your samples. As far as temperature staying "constant" I don't mean that it remains the same temperature all day. What I mean is that all samples are experiencing the same temperature regime (fluctuations throughout the day, etc). The same goes for humidity.

As Mith mentioned, your n will probably not be high enough for any statistically valid result. Statistical validity may not be your goal, but if it is, then I suggest increasing the amount of times you repeat your process or increasing the number of plants in each variable (ie put 10 plants in the cupboard instead of 1)

As it is, even if you had gotten the results you hypothesized, you could not draw any conclusions from them. (assuming you've only repeated the process once)
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Postby RLBallantyne » Tue Aug 21, 2007 6:47 pm

Seal off the containers that have the plants in them. I doubt the veg. oil on top is a good seal.

I'd suggest flasks. Cut rubber stoppers in order to wrap them around the stems and seal, perhaps with parafin, but be careful not to overheat the stems material.
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