This practical was developed for the Scottish Highers and is in the appropriate format, but the protocol can equally well be used for other UK specifications.
In this practical experiment, students look at how at potometer can be used to measure factors affecting transpiration rates, and develop investigations to compare the transpiration rates under different circumstances.
A potometer is a piece of apparatus used to measure the rate of water loss from a plant (transpiration). The rate of transpiration can be estimated in two ways:
1) Indirectly - by measuring the distance the water level drops in the graduated tube over a measured length of time. It is assumed that this is due to the cutting taking in water which in turn is necessary to replace an equal volume of water lost by transpiration.
2) Directly - by measuring the reduction in mass of the potometer over a period of time. Here it is assumed that any loss in mass is due to transpiration.
In this practical, you will set up a potometer and then place it in different situations, changing one environmental factor at a time, such as light intensity, temperature, wind levels etc.
Download the full protocol from the link on the right.