Investigating the rate of transpiration
Practical SBA task
A group of Grade 10 learners investigated the effect of environmental factors on the rate of transpiration. They set up an experiment as shown in the diagram below.
lamp air bubble
Apparatus used to investigate the rate of transpiration
1.1 1.2 1.3 1.4
State a hypothesis for this investigation. Name the apparatus used in this investigation. What is the significance of the tap? Explain TWO precautions that the learners must take to ensure that the results are reliable. In the investigation on transpiration, measurements of the distance travelled by the air bubble in the capillary tube were taken every minute. The opening of the capillary tube had an area of 4 mm2. Study the table below of the results obtained, and answer the questions that follow. Time (minutes) 1 2 3 4 5 1.5.1 Use the equation, Volume of water displaced = distance along capillary tube x area of capillary tube opening, to calculate the volume of water displaced at the second minute. 1.5.2 During which minute did the transpiration rate decrease? Distance travelled by air bubble along capillary tube (mm) 4 11 18 30 22
(3) (2) (2)
List the (a) (b) dependant variable. independent variable. (2) (2)
The apparatus was also used to measure the rate of water loss at several light intensities. At each light intensity the apparatus was left for 15 minutes before starting the measurements. The results are shown in the table below.
Light intensity Loss of water (kilolux) (g/hour) 0 1 10 15 20 20 30 25 40 25 1.7.1 1.7.2 Draw a line graph to present the data shown in the table. Why is the apparatus left for 15 minutes at each new light intensity before starting the measurements? What evidence supports the statement that the stomata are fully open at a light intensity of 30 kilolux? Predict what would be the effect on the results if the...