PAGs

Question 1

PAG 5.3 Transpiration method

Answer 1

Cut a shoot at a slant under water to prevent air from entering the xylem
Slanted cut increases surface area for water uptake
Assemble potometer u Dee water and inset shoot underwater so no air can enter
Remove aparatus from the water but keep the end of the capillary tubing submerged in water
Check apparatus is water tight and airtight (can use Vaseline at joints to achieve this)
Dry leaves and allow time for shoot to acclimatise before shutting the tap
Remove the end of the capillary tube from the beaker of water until one air bubble has formed, then put end of the tube back in the water
Record starting position of air bubble
Start a stopwatch and record the distance move by the bubble per unit of time (e.g. per hour)
Rate of air bubble movement is an estimate for the rate of transpiration
Only change one variable at a time (e.g. temperature)
All other conditions (e.g, light and humidity) must be kept constant