The UMass football and basketball players who have taken Botany for Gardeners during the summer online (to satisfy their Biological Sciences-BS General Education Requirement) know the answer to this question!
Whats the difference between a common, white (Irish) potato and a sweet potato? This is not only an interesting dinner conversation topic, but a fundamental principle of biology!
The sweet potato is a swollen root. In tropical and sub-tropical climates (where it grows naturally) the sugars and carbohydrate stored in this swollen root help the plant survive during a dry season. When it gets dry, the leaves die down. When the rains return, the leaves begin to regrow right out of the roots. Here is what it looks like.
The common (Irish) potato is NOT a root!
This potato is actually an underground stem. It is also a storage organ, which helps the plant survive during cold weather (the potato is native to the Andes Mountains in Peru – where it can get really cold) rather then dry weather.
We can tell the potato is NOT a root, because if you put a white potato in the sun it will turn green on the sunny side (see below). Roots can’t do that!
Don’t eat the green however! When potatoes are left in the sun, they form an alkaloid called solanine which is toxic (although you would have to eat A LOT to make you sick). The bitter taste however protects the plant from being eaten by animals!
Of course, you have probably also seen what happens when potatoes are stored too long. These underground stems, will begin to sprout new shoots!
What’s the difference between a common potato and a sweet potato? Now you know!
To learn more about plants and knock off a GenED, why not take Botany for Gardeners!