Lesson 4: Transpiration

Introduction /Theme:

Students will participate in a hands-on activity to visualize the process of transpiration. Students will collect and monitor the amount of water expelled by various leaves on local plants as a result of transpiration. Students will hypothesize factors that impact transpiration rates and compare this information to the data and graphical analysis completed from a similar research study in Brasilia, Brazil.

Learning outcomes:

The student will select leaves at different depths in the forest to determine the sunlight availability differences. Students will set up a transpiration monitoring system and measure the amount of water released by transpiration at different sunlight levels.

Curriculum alignment:

6th grade

• 1.06 Use mathematics to gather, organize, and present quantitative data resulting from scientific investigations: measurement, analysis of data, graphing, prediction models.
• 1.09 Use technologies and information systems to: research, gather and analyze data, visualize data, disseminate findings to others. (if optional technology is used during this lesson)
• 7.02 Investigate factors that determine the growth and survival of organisms including: light, temperature range, mineral availability, soil/rock type, water, energy

Classroom time required:

3 class periods double block or 5 regular class periods

Materials needed:

• Calculator
• Graduated cylinders, 100mL
• Graph paper
• Parafilm
• Plastic sandwich bags (without Ziploc seal)
• Sunlight plot (see attachment)
• Computer access with Microsoft Excel (optional)

Technology resources:

Optional computer access with Microsoft Excel

Pre-activities:

Have students point to Brazil on a world map (either a map in the classroom, textbook, or student agenda). Instruct students to identify the capital of Brazil (Brasilia) on their map. Teacher walks around to assist students and provide positive verbal feedback.

Activities:

Warm-Up

The teacher says or posts:
Imagine you are a scientist in Brasilia, Brazil conducting research. It’s a warm day in June and you have consumed all of your water. You are very thirsty. There is no water source nearby, nor do you have any friends or fellow researchers nearby to provide you with extra water. You still have 2 more hours in the field doing research and desperately need water. What will you do?

Teacher may make picture of Brasilia research station available for students to view to help make the situation more realistic. Students will work in groups of 2-4 and describe with words and pictures what they would do if they were in this situation. Students will share their proposal to the class. The teacher will not say “right” or “wrong,” as it is beneficial to the students to encourage the process of inquiry and not be the source of correct answers for students. Let them discover the answer in the following activity.

Transpiration Laboratory

See attached lab. It is up to the teacher discretion to describe the process of transpiration prior to this activity; however, this activity will allow students to discover this process on their own. It is recommended that the teacher describe this process as transpiration after the students have observed and discovered this process on their own. Special note to teacher: If the volume of water collected during the lab is minimal, consider recording the mass of the bags before the experiment and throughout the experiment to determine the volume of water.

Assessment:

Warm-up: Participation grade

Laboratory:

• Title: 3 points
• Introduction: 10 points (complete grammar and sentences recommended)
• Materials: 12 points
• Methods: 10 points
• Data Collection: 15 points
• Results - Written: 15 points
• Results - Data & Figures: 15 points
• Discussion: 20 points (10 points sentences, 5 points illustrations, 5 points key words)

Critical vocabulary:

X-axis, Y-axis, origin, data, transpiration