How to Get an Onion to Grow Root Tips in Water

Mitosis is a process of cell division, whereby the separation creates two identical daughter cells, each comprised of the full number of chromosomes. In the lab, students can put onion roots under a microscope to observe the various stages of the process. Onion roots are an ideal specimen to witness the process, because the roots are easy to grow in large numbers, the cells actively divide at the root tips, various stages of the mitosis occur simultaneously and the tips of the onion roots fit under a microscope easily. To observe the process, first grow onion roots tips in water.

Onion bulb
Glass
Knife
3 toothpicks

Instructions

- 1
  Fill a small glass with water. Select a glass that is slightly larger than the onion bulb.
- 2
  Hold the onion in your hand, so that the tip of the onion is up and the root section down. Do not remove the onion’s skin.
- 3
  Cut around the root section, shaving off the outer layer of the roots, without removing the roots completely.
- 4
  Insert a toothpick in the side of the onion, so that it is perpendicular to the onion. Push the toothpick into the bulb about 1/4 inch, just so it is firmly in the onion.
- 5
  Poke two more toothpicks into the middle of the onion. Equally space the toothpicks around the middle section of the onion. The purpose of the toothpicks is to suspend the onion over the water, in a similar fashion that you use when suspending an avocado seed.
- 6
  Set the onion in the glass of water, root end first. The tips of the toothpicks should rest on the rim of the glass, suspending the onion over the water. Only the bottom third, root end of the onion should be in the water.
- 7
  Place the glass in the light, yet not in direct sunlight. Maintain the level of the water, so that the root end of the onion stays wet as the root tips grow.

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