How to set up a potometer to ensure valid measurements

• 1) Immerse the apparatus in water to fill up the capillary tubing and water reservoir with water, ensure there are no air bubbles in the apparatus tubing, to stop air bubbles entering the xylem vessels
• 2) Cut 2-3cm off the cut end of the stem of a healthy leafy shoot underwater, at a slanted angle to increase the surface area for water uptake and insert the shoot into the apparatus underwater
• 3) Remove the potometer from the water and put an airtight and watertight joint around the shoot; could use Vaseline (but be careful not to block up the ends of the xylem vessels with grease), then dry leaves carefully
• 4) Ensure other environmental factors are controlled (temperature, wind speed, light intensity and humidity) and allow time for the shoot to acclimatise to the environmental conditions (5-10 min)
• 5) Shut the tap of the water reservoir and record the position of the air bubble/meniscus on the ruler scale, start timing and leave for known time period (e.g. 10min) then record the new meniscus position and calculate distance moved per unit time
• 6) The experiment should be repeated at least three times in order to calculate a mean and identify anomalous results; makes the results more reliable and reproducible