Turnips

The most common type of turnip is mostly white-skinned apart from the upper 1–6 cm, which protrude above the ground and are purple or red, or greenish wherever sunlight has fallen. This above-ground part develops from stem tissue, but is fused with the root. The interior flesh is entirely white. The entire root is roughly globular, about 5–20 cm in diameter, and lacks side roots. The taproot (the normal root below the swollen storage root) is thin and 10 cm or more in length; it is trimmed off before marketing. The leaves grow directly from the above-ground shoulder of the root, with little or no visible crown or neck (as found in rutabagas).The turnip or white turnip (Brassica rapa subsp. rapa) is a root vegetable commonly grown in temperate climates worldwide for its white, bulbous taproot.
Like rutabaga, turnip contains bitter cyanoglucosides that release small amounts of cyanide. Sensitivity to the bitterness of these cyanoglucosides is controlled by a paired gene. Subjects who have inherited two copies of the “sensitive” gene find turnips twice as bitter as those who have two “insensitive” genes, thus may find turnips and other cyanoglucoside-containing foods intolerably bitter.