Lenticel is a small cork pore, or narrow line, on the surface of woody plant stems. According to the Free Dictionary, it functions as a pore allowing for the interchange of gases between the interior tissue and the surrounding air. Internal plant tissue is impermeable to gases without lenticel.
According to Wikipedia, the name lenticel derives from its lenticular shape. The shape of lenticel is one of the characteristics used for tree identification. Lenticel is the raised circular, oval or elongated areas on plant stems and roots. Observers describe them as warts, bumps, splits or fissures. All trees have lenticel, although some is more conspicuous than others. As stems and roots mature, lenticel development continues in the new bark or root. The color, shape and size of lenticel depend on the species of tree or plant.
Wikipedia states that lenticel is present on fruits such as apples, pears and avocados. On pears, it serves as an indicator of when to pick a fruit because lenticel darkens as the fruit ripens. Some bacteria and fungus penetrate fruits through their lenticel. Lenticel is also present on potato tubers. In wet soil, lenticel on potato tubers proliferates, while in dry soil lenticel become smaller. Lenticel increases at a greater rate on potatoes stored for a long period of time.