Activity 4: Transpiration
SUCK IT UP! A STUDY OF TRANSPIRATION
Transpiration and water movement through plants play an important role in the hydrologic cycle. The activity shows how transpiration relates to weather conditions.
Instructional Method: Experiment
Goal: To show students how plants perform a vital part in the hydrologic cycle.
Objectives: Students will be able to:
Set up: 5 minutes
Surface water such as lakes and oceans is not the only place from where water vapor comes. Plants are instrumental in moving water within the ground up to the surface. Transpiration is the act of liquid water changing into water vapor on the surface of a plant. It is similar to evaporation, only more difficult to observe, and takes place ONLY on plants. Plants move water through small "vessels" that are stacked one on top of the other, like a giant soda straw. As water is removed from the top of the straw through transpiration, more water must move up the straw to take its place.
Image by Hailey King, NASA
As the sun transpires water from the leaves of a plant, more water must move from the branches into the leaves to take its place. As this water moves onto the leaf, more water must move from the roots, to the trunk, to the branches. The source for water in plants is moisture in the soil. Thus, plants are able to bring water from the ground into the atmosphere.
Water is released from a plant during photosynthesis (a plant's process for making food, utilizing the sun's energy and carbon dioxide). The water is released through openings on the underside of the plant called stomata. These stomata are only open during photosynthesis. Therefore, stomata are only open during the day while the sun is shining and evaporation of water from the surface of the leaf can take place. If the surrounding air is dry, more water evaporates from the open stomata than if the air is humid.
In this activity we will see water transpiring off of a plant and explore its relationship with other weather conditions.
How much water was collected? From where did the water come? Which branch produced the most water? Why? Does the amount of sun make a difference? Was it cloudy on any of the days we collected water? What happened when it was cloudy? If we wouldn't have collected the water, where would it have gone? How is transpiration different from evaporation? What happens to the water that is in the air?
If you are short on time, or your students want to explore the concept further, check your tree bags three times a day, early morning, at noon and late in the afternoon. Explore whether the time of day creates a difference in water production and why.
Included National Parks and other sites:
Bryce Canyon National Park
Utah Science Core:
2nd Grade Standard 2 Objective 1