Prepare A Temporary Mount of the Onion Root Tip To Study Mitosis

Aim

To study mitosis by preparing a temporary mount of an onion root tip.

Necessary Materials & Apparatus

• Onion
• Watch glass
• Glass slide
• Filter paper
• Aceto-alcohol
• Coverslip
• Water
• N/10 Hydrochloric acid
• Acetocarmine Stain
• Burner
• Forceps
• Dropper
• Blade
• Needle
• Compound microscope

Procedure

• Place the onion on a tile
• Using the blade, remove the dry roots
• Regrow the root tips by placing the bulbs in a water-filled beaker
• After 3 to 6 days, new roots may emerge
• Slide 2 to 3 cm off freshly grown roots and place them on a watch glass
• Use a forceps to transfer the freshly cut tips to a test tube containing Aceto-alcohol (1:3 = anhydrous acetic acid: ethanol)
• Submerge the root tips in the solution for 24 hours
• Use the forceps to take out a single root and place it on a glass slide.
• Put a single drop of N/10 HCl on the root tip
• Then, put 2-3 drops of acetocarmine stain
• Use a burner to warm it, and ensure that the stain does not dry up.
• Use a filter paper to blot out the excess stain, if any
• Cut the significantly stained portion of the root using a blade and place it on a slide. Discard the rest of the root
• Put a drop of water on the root tip
• Place a coverslip using a needle
• Tap the coverslip such that the meristematic tissue of the root tip is compressed and spread out as a thin layer.
• The preparation is ready for studying mitosis.

Observation

Use the compound microscope to study the various phases of mitosis.