Above Image: Close up of a leaf with breathing cells © defun, iStockphoto.com
Students will be introduced to the leaf structures of dicots and their role in gas exchange. Students will collaborate to perform an inquiry in which they follow a simple procedure to collect leaf cells samples and compare leaf structures from different plants.
Inquiry Skill Development
- To introduce the structures of the leaf system
- To understand the role of cells of the leaf system in the process of gas exchange in plants
Prior Knowledge and Skills
- Basic plant anatomy
- Understands the concept of cells
- Can operate a simple microscope
- Obtains a usable leaf cell sample
- Observes leaf cells using a microscope
- Accurately records observations in a labelled, hand-drawn diagram
- Understands the role of leaf cell structures and their function in the process of gas exchange
- 40 – 60 minutes in class
- Time may be required prior to lesson to read background information
- Microscope - 1 per group of 3-4 students
- Microscope slides - 1 per group
- Clear nail polish - 1 bottle per group
- Clear tape - 1 roll per group
- Tomato plants from Tomatosphere™ Investigation, 1-2 leaves from control plants (Earth seeds) and 1-2 leaves from treatment plants (space seeds)
- Optional – monocot leaves (e.g., grass, corn leaves) for the purpose of comparing to dicot leaves
- Specialized Cells of the Leaf System (Tomatosphere™ Backgrounder) – 1 per student
- BLM1: Inquiry Summary: Where does gas exchange take place in plants? - 1 per student doc pdf
- BLM2: Leaf Cell Sampling Procedure - 1 per group doc pdf
Tips for Success
- Organizing the working groups prior to the lesson is highly recommended to save time.
- Background reading and/or video viewing may be assigned prior to class in preparation for the inquiry in-class discussions.
Introduction to the Inquiry
Have students read Specialized Cells of the Leaf System (Tomatosphere™ Backgrounder) as a pre-class reading assignment.
Organize students into working groups of 2 to 4. Distribute one copy of BLM1: Inquiry Summary to each group.
Have each student group develop a testable question for an inquiry that compares the stomata from the two Tomatosphere™ plant leaf samples using a leaf cell sample and a microscope and the skill of Observing (e.g., compare the number, shape, etc. of stomata or cell configuration). Have each group of students also develop a hypothesis based on their inquiry question.
Optional Minds-On activity
Have students watch the video Creating Testable Questions or read the science processes section on Asking Testable Questions on Tomatosphere™ if they need practice with developing testable questions.
Conduct the Inquiry: Where does gas exchange in plants take place?
Distribute the materials to each group. Each group will be working with TWO leaves - ONE Tomatosphere™ leaf from each of the TWO treatment groups. If you are not using the Tomatosphere™ plants, give each group two different types of leaves (e.g., a dicot leaf and a monocot leaf).
Note: To avoid mix-ups regarding the identity of the leaves, you may wish to hand out one leaf at a time and have the groups prepare and label a slide sample for one leaf before you hand out the second leaf.
Provide each group a copy of BLM 2: Leaf Cell Sampling Procedure or project the instructions on a screen using the technology available in your classroom.
Familiarize yourself with the leaf cell sampling procedure and tips for success as outlined below:
- Gently remove a leaf from one of the groups of tomato plants (e.g., control or test group).
- Gently paint a thin layer of clear nail polish over the top surface of the leaf and allow it to dry completely.
- Press a piece of clear tape over the dried nail polish. Carefully remove the tape. The thin layer of nail polish should stick to the tape and pull away from the surface of the leaf.
- Press the tape onto a microscope slide. Label the slide to indicate the type of leaf (e.g. control or test, or Type G or H, or monocot vs. dicot, etc.)
- Examine the slide under microscope.
- Repeat Steps a to e with a leaf from the other group of plants.
Using BLM1: Inquiry Summary, have students record their observations and draw the cell structures they can see in the slide samples in the blank spaces provided in the inquiry summary. Instruct students to label their drawings using the correct terminology. (See Figure 1)
At the end of the inquiry, review the results and conclusions students recorded on BLM1. Have students discuss the results in relation to the testable questions and hypotheses they developed at the start of the activity.
Students can follow-up the inquiry by reading this Let’s Talk Science article, Canadian Light Source Synchrotron takes Tomatosphere™ to the next Level, about students who found some interesting differences between the test and control Tomatosphere™ plants in inquiries they conducted at the Canadian Light Source Synchrotron in Saskatoon.
- Repeat the activity using different types of leaves (e.g., from plants other than tomatoes or monocot leaves), or leaves from different parts of the same plant.
Let’s Talk Science Resources:
The Tomatosphere™ team is interested in collecting exemplars and photos of our learning strategies in action. Please consider sharing with us at: firstname.lastname@example.org