PART 4: Plant Transpiration

1) Prepare prior to class time two small potted plants (purchase or prepare at home or use from the schools supply - they can be returned unharmed after the demo is completed). Plants should have numerous stems and leaves but no taller than 8 to 10 inches including pot height and the soil or peat should be moist. Conditions for the two plants should be as similar as possible.

2) Place a plastic bag over one of the plants and secure with a rubber band.

3) Let stand overnight near a warm spot so as to allow moisture to escape the leaves and condense on the inside surface of the plastic. See Figure 4

Conclusions

This is evidence that the plant is breathing - taking in water from the soil and giving off water to the air at the same time that it is taking in carbon dioxide and giving off oxygen.

How does this happen?

Discuss the relationship of the diagram and labeling of their plants to what is happening when the moisture collects on the surface of the plastic.