A doctor will determine the underlying cause of dry mouth in the patient and then take steps to minimize the underlying cause, such as stopping a medication causing the dry mouth. For many individuals, however, little can be done to alter the underlying cause.
The carrot (Daucus carota subsp. sativus) is a root vegetable, usually orange in colour, though purple, red, white, and yellow varieties exist. It has a crisp texture when fresh. The most commonly eaten part of a carrot is a taproot, although the greens are sometimes eaten as well. It is a domesticated form of the wild carrot Daucus carota, native to Europe and southwestern Asia. The domestic carrot has been selectively bred for its greatly enlarged and more palatable, less woody-textured edible taproot.
Root tubers are usually defined, as in the article, as modified lateral roots, whereas storage tap roots, as in carrots, are not lateral. But it's not clear to me that this is really a fundamental difference, nor that the terms are always used consistently.