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Q. How does a potometer work?


Hi there Bob and welcome to homework high.

So here is how the potometer works.

The potometer is filled with water by opening the tap. Under water, a shoot of a plant is cut and put into the potometer on the left hand side. If this was done in air a bubble of air might get in the xylem vessel and the experiment would not work. The tap is then closed and a bubble of coloured dye is injected in the capillary tube. Now as the plant looses water, the water lost is made up by water in the capillary tube which sucks the coloured bubble along. So if you time how long the bubble takes to travel a certain distance it will provide you with the rate of transpiration. You can vary the condidiions, like putting a fan next to the plant and see if that makes a difference to the transpiration rate.

Submitted by: Bob, (Age 13)

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