AP Biology students conduct whole plant transpiration lab

Students in Mrs. Emily Cloud’s AP Biology class conducted a series of labs on the transpiration of plants. Objectives for the lab included:

• To understand how water moves from roots to leaves in terms of the physical and chemical properties of water and the forces provided by differences in water potential.
• To understand the role of transpiration in the transport of water within a plant.
• To understand the structures used by plants to transport water and regulate water movement.
• To test the effects of environmental variables on rates of transpiration using a controlled experiment.

The procedures included weighing the plant each day for an entire week. Four control groups were created in which the first group was placed in front of a fan, the second group was placed in bright light, the third group was misted and covered with a 10-gallon aquarium, and the fourth group was placed in a dark cabinet.

The rate of transpiration is measured as the amount of water lost per square meter per minute. Because water evaporates through the many stomata on the leaf surface, the rate of transpiration is directly related to the surface area.

Results included determining the percent change in mass throughout the week. Students then graphed the change.

On the lab, SPCHS Senior Lauren Skinner said, “What I found most surprising about the lab was how factors such as light and wind affect plant transpiration. Even a little bit of wind or light can affect the plant in a way larger than you would have thought.”