What Effect Does Iodine Have on Onion Cells?

What Effect Does Iodine Have on Onion Cells?

What Effect Does Iodine Have on Onion Cells?

Iodine reacts with the starch present in onion cells, producing a coloration that makes the cells easily visible under a microscope. Onion cells are naturally transparent, so it is difficult to properly visualize them without using a solution to increase contrast.

To obtain a clear image of onion cells, a wet mount microscope specimen must be prepared first. The person preparing the specimen must place a drop of water on a clean microscope slide, then place a piece of onion skin on it. To ensure contrast, a drop of iodine solution is added. The specimen is then protected with a cover slip and observed under the microscope. If the specimen contains a higher amount of starch, adding iodine creates a blue coloration.