Study Mitosis with a Temporary Mount of an Onion Root Tip

The goal of this experiment is to observe the process of mitosis by creating a temporary mount of an onion root tip.

• An onion bulb
• Watch glass
• Microscope slide
• Absorbent paper
• Aceto-alcohol solution
• Cover glass
• Clear water
• N/10 Hydrochloric acid
• Acetocarmine Stain
• Heating device
• Tweezers
• Pipette
• Sharp knife
• Needle
• Binocular microscope

• Position the onion on a flat surface
• With the knife, discard the dry roots
• Encourage new root tips to grow by immersing the bulbs in a beaker filled with water
• In about 3 to 6 days, new roots should sprout
• Cut off 2 to 3 cm of the newly grown roots and put them on a watch glass
• Transfer the freshly cut tips into a test tube filled with Aceto-alcohol (1:3 = anhydrous acetic acid: ethanol) using a pair of tweezers
• Soak the root tips in the solution for one day
• Using the tweezers, pick up a single root and place it on a microscope slide.
• Add a single drop of N/10 HCl to the root tip
• Next, add 2-3 drops of acetocarmine stain
• Warm it using a heating device, ensuring the stain does not dry.
• If there is any excess stain, blot it out using absorbent paper
• Slice the heavily stained part of the root with a knife and place it on a slide. Discard the remaining part of the root
• Add a drop of water to the root tip
• Use a needle to place a cover glass
• Press the cover glass so that the meristematic tissue of the root tip is flattened and spread out into a thin layer.
• The preparation is now ready for mitosis study.

Utilize the binocular microscope to study the various stages of mitosis.