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Name: Bernadette
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Hi! I am a high school student who is doing a science project concerning the transpiration of plants. My question is "Do plants transpire at the same rate under different sources of light?" For my experiment I am planning to use 6 pansies and plant them in 6 2-liter bottles by cutting off 2/3 of the top. After planting them and watering them I will reattach the tops to the bottoms and place one under an incandescent lamp, one under fluorescent light, and the control under natural sunlight (the three others I will use to repeat my steps for more accurate results). After three hours I plan to remove the tops the measure the amount of water.

Now, what I am wondering is do you have any suggestions on how I could show my results? In the procedure, do you see anything I should change? I also read that heat and humidity affects transpiration how would I be able to tell how much the light alone affected the plants?

Something I would consider is that evaporation is not being controlled. You might try setting up a simple transpirometer, placing the stem of your sample plant into a tube with water that is otherwise sealed. Measure the amount of water lost from the tube - it could only leave via transpiration. You also need to control for surface area of the leaves - you might need to find a way to convert the mass of the leaves to surface area, or trace each leaf onto graph paper and measure the surface area by measuring the space on the graph paper.
Good luck -

ellen mayo

Dear Bernadette,

The following may be helpful.


Anthony R. Brach

When beta decay occurs, the electron produced has quite a lot of kinetic energy. Enough, in fact, to exceed the attraction between the newly-produced electron and proton, so the electron flies away.

Rich Barrans
Argonne National Lab

As with all science experiments, the key is to keep all the variables but one the same, if heat, humidity, and all other conditions except the light are the same, then results must be due to the different light.

J. Elliott

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