AP Exam preparation -- Doing the AP version of this lab:
Please read through the 2012 AP Biology Lab Manual, Investigation #11: Transpiration. This lab presents very few problems for students to acquire materials. However, if you are able to arrange to perform the AP lab with a local homeschool group or a biology tutor, then you should do so.
If you are actually unable to carry out the measurements for Investigation #11, you may directly observe plant transpiration using the method below.
You could repeat this experiment several times, using fresh celery each time, but vary the solution in the red jar:
If you notice a difference in absorption between your pure water source and the solution, you may want to vary the concentration of the solution to see what affect concentration has on the rate of absorption.
Repeat this experiment at least once, using different bean plants in one of the following treatments:
Describe your procedures and equipment.
For the "gross observation", describe your observations of absorption of dye by the celery. Which solutions increased the rate of absorption? Which decreased the rate of absorption over distilled water?
For the "close measurement", determine water loss as change in water level in ml for the intervals, divided by the total leaf surface area.
Plot the values as water loss as a function of time, using different colors for your "control" plot and your "treatment" plot.
Determine the rate of water loss in ml/min for each situation.
Explain why the difference in water loss exists. How does heat or light , air circulation, or humidity affect water loss.
Suggest adaptations that keep the plants from losing water.
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