How does the reaction of iodine with potato cells compare with onion epidermis?
James Williams
Published Apr 25, 2026
Regarding this, what does this tell you about the differences between the storage products in onions and potatoes?
-The onion cell does not have starch storage so it wouldn't be stained the dark purple. This tells us that the storage products in potatoes contain starch and the onion storage products do not contain starch within them.
Subsequently, question is, what part of the onion cell did the iodine stain? The layers of an onion contain simple sugars (carbohydrates) some of which are stored as starch (starch granules). Given that iodine tends to bind to starch, it stains the starch granules when the two come in to contact making them visible.
Accordingly, why is iodine used to stain onion cells?
Because iodine will bind to starch granules, iodine can be used as a stain to visualize the cytoplasm of yellow and white onions (a step that is unnecessary with red onions, which are naturally pigmented).
What does iodine stain in potato cells?
iodine is the indicator of starch. and starch is a compound found in potato (actually in most of the plant cells).