2.47 describe experiments to investigate the role of environmental factors in determining the rate of transpiration from a leafy shoot

2.47 •cut a shoot underwater to prevent air from entering the xylem. 

                  •cut it at a slant to increase the surface area available for water uptake

       

        •assemble the potometer in water and the shoot underwater, so no air can enter in

       

        •remove the apparatus from the water but keep the end of the capillary tube submerged in beaker of water

                  •check everything is water and air tight

       

        •dry the leaves and allow time 

       

        •remove the end of the capillary tube from the beaker of water until one air bubble has formed, the put the end of the tube back into the water

       

        •record the starting position of the air bubble 

       

        •start a stopwatch and record the distance moved by the bubble per unit of time

      

        •keep the conditions constant throughout the experiment e.g the temperature and air humidity 

       •light intensity: •use the lamp to increase and decrease light intensity using a lamp and a box

       •temperature: •put the potometer in a room warmer or colder than the original experiment

       •humidity: •spray water in a clear plastic bag before sealing it, decreasing the rate

       •wind speed: •use a fan to increase the wind speed, increasing the transpiration rate