Onion root tip mitosis experiment and observation of stages

Introduction

This tutorial will guide you through the process of observing mitosis in onion root tips. By preparing a temporary slide, you will be able to study the different stages of mitosis under a microscope. This experiment is a common part of the Class 12 Biology syllabus and will help you understand cell division through practical application.

Step 1: Growing and Harvesting Onion Root Tips

• Obtain onion bulbs and place them in water-filled containers.
• Allow the roots to grow for several days until they are about 2-3 cm long.
• Carefully harvest the root tips using sterile forceps.

Step 2: Fixing the Onion Root Tips

• Store the harvested root tips in a solution of 70% alcohol for long-term preservation.
• Prepare a fixative using equal parts of acetic acid and alcohol (1:1) and immerse the root tips for one hour.

Step 3: Preparing the Microscope Slide

• Take a fixed root tip from the solution and rinse it with water on a clean microscope slide.
• Use blotting paper to remove excess liquid before proceeding.

Step 4: Hydrolyzing the Root Tip

• Add 2 to 3 drops of 1 N hydrochloric acid (HCl) to the root tip on the slide.
• Allow the HCl to act for a few minutes to hydrolyze the extracellular material.
• Remove the HCl using blotting paper to halt its effect on the root tip.

Step 5: Staining the Onion Root Tip

• After hydrolysis, add Aceto-carmine stain to the root tip.
• Add 2 more drops of the stain to ensure the tissue remains moist.
• Rinse the root tip with water and use blotting paper to remove excess stain.

Step 6: Mounting the Slide

• Place a drop of glycerin on the stained root tip to prevent drying.
• Carefully cover the tissue with a coverslip using a sterile needle.

Step 7: Focusing and Observing Under the Microscope

• Start with a 4x objective lens to locate the cells.
• Switch to a 10x objective lens to focus more clearly.
• Identify the stages of mitosis: prophase, metaphase, anaphase, telophase, and cytokinesis.

Conclusion

You have now completed the onion root tip mitosis experiment! By following these steps, you can effectively prepare a temporary slide and observe the different stages of mitosis. This practical experience enhances your understanding of cell division and its significance in biology. For further exploration, consider comparing the mitosis stages in other plant tissues or conducting similar experiments with different stains.