measuring plant growth – long experiment

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A position sensor can be attached to a plant to record its growth. Depending on the plant chosen this is a very slow process. Using a sensor greatly decreases the time taken before the results can be used. It is possible to compare the effects of light and dark and other factors on plant growth. Ideally, two plants and two position sensors would be used. In order to allow a longer period of measurement the experiment is best performed using a position sensor attached to a data logger as described below.

Apparatus
Clamps and stands, plant, such as a growing bean and thread, data logger and position sensor.

Setting up
Set up the position sensor and plant. Use thread to tie the plant to the position sensor. If the sensor is placed the ‘other way’ round, the graph will develop in the opposite direction.

Recording the data
Connect the sensor to socket 1 on the data logger.
Press the button on the data logger that starts it recording.
Transferring data to the computer
Connect the data logger to the computer. Get the software to transfer data from it.

Using the results
How is plant growth shown on the graph?
What does the graph tell you about plant growth? Is it steady – or does its rate change during the day or night?
What sources of error can you see in this experiment?
Save your data on disk. Print the graph.

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