the shoot and on the hydrose of the tissue, which refers to the internal moisture. As stems and roots mature lenticel development continues in the new periderm (for example, periderm that forms at the bottom of cracks in the bark). Lenticels are found as raised circular, oval, or elongated areas on stems and roots. In woody plants, lenticels commonly appear as rough, cork-like structures on young branches. Underneath them, porous tissue creates a number of large intercellular spaces between cells. This tissue fills the lenticel and arises from cell division in the phellogen or substomatal ground tissue. Discoloration of lenticels may also occur, such as in mangoes, that may be due to the amount of lignin in cell walls. In oxygen deprived conditions, making respiration a daily challenge, different species may possess specialized structures where lenticels can be found. For example, in a common mangrove species, lenticels appear on pneumatophores (specialized roots), where the parenchyma cells that connect to the aerenchyma structure increase in size and go through cell division. In contrast, lenticels in grapes are located on the pedicels and act as a function of temperature. If they are blocked, hypoxia and successive ethanol accumulation may result and lead to cell death. Fruits Lenticels are also present on many fruits, quite noticeably on many apples and pears. On European pears, they can serve as an indicator of when to pick the fruit, as light lenticels on the immature fruit darken and become brown and shallow from the formation of cork cells Certain bacterial and fungal infections can penetrate fruits through their lenticels, with susceptibility sometimes increasing with its age. As mentioned previously, the term lenticel is usually associated with the breakage of periderm tissue that is associated with gas exchange; however, lenticels also refer to the lightly colored spots found on apples (a type of pome fruit). "Lenticel" seems to be the most appropriate term to describe both structures mentioned in light of their similar function in gas exchange. Pome lenticels can be derived from no longer functioning stomata, epidermal breaks from the removal of trichomes, and other epidermal breaks that usually occur in the early development of young pome fruits. The closing of pome lenticels can arise when the cuticle over the stomata opening or the substomatal layer seals. Closing can also begin if the substomatal cells become suberized, like cork. The number of lenticels usually varies between