Stages of Mitosis in Onion Root Cells

Activity 2: Pre-Assessment

1. In a plant, where would you likely find cells that are actively undergoing mitosis? Where would you likely find cells that aren’t actively undergoing mitosis? Explain your answers.
2. Think about how a plant grows. In which parts of the plant would many cells likely be undergoing mitosis?
3. Discuss the answers to the questions with a partner (think, pair, share) and then the class.

Activity 2: Observe the Stages of Mitosis in Onion Root Cells

Plant cells also use mitosis for growth, maintenance, and repair. The plant’s cell wall, as well as the nuclear material, makes observing mitosis much easier. Figure 13.5 shows some of the similarities and differences between plant and animal mitosis. For example, during cytokinesis, an animal cell pinches apart into two daughter cells, while a plant cell develops a new cell wall, called a cell plate, between the new daughter cells.

Safety Precautions

• Be careful handling glass slides, as the edges may be sharp.
• Observe proper use of the microscope; avoid handling the electric cord with wet hands.
• Do not use the coarse adjustment knob of the microscope at higher magnifications.
• Inform your teacher immediately of any broken glassware, as it could cause injuries.

For this activity, you will need the following:

• Prepared microscope slides of stained onion root tips or online images and resources

  

This video provides a demo of materials including onion or garlic bulbs, germination of root, preparation of root tip, staining, and observing under the microscope:

For this activity, you will work in pairs.

Structured Inquiry

Step 1: Hypothesize/Predict: In your notebook, hypothesize what regions of the onion root tip might differ in the number of cells undergoing mitosis. What is your reasoning behind this hypothesis? Record your answers in your notebook.

Step 2: Student-Led Planning: In your notebook, make a drawing of each phase of mitosis, as well as interphase, in a plant cell. Label, in each drawing, the defining features that you will look for when identifying each stage under the microscope.

Step 3: Critical Analysis: Are the predictions you made in Step 1 supported by your observations? Why do you think cells undergoing mitosis in the onion root cell are distributed the way they are? What differences between plant and animal cells are visible under the microscope slide?

Assessments

1. Describe some similarities and some differences between animal and plant mitosis.
2. Based on your observations, explain how onion roots grow at the cellular level.