Lenticels are air spaces open to the outside environment.

Since the above-surface roots of mangrove trees function partly in the uptake of oxygen, most of them contain air spaces called lenticels which are open to the outside environment. Lenticels are areas within the outer layer of tissue in which cell division is more active then elsewhere, and this results in the formation of the tissue rich in air spaces.

The soil of the mangrove forest and the seawater which bathes the trees' roots contain high concentrations of salt, which presents physiological problems for any plant growing there. Although most mangrove species can tolerate greater concentrations of salt in the sap than can most land plants, different mangrove trees have developed a number of different mechanisms for dealing with the salt. Most species seem to be able to exclude most salt by special physiological adaptations in their roots which actively return salt to the environment, so the sap in these trees is much less salty than the water surrounding the roots. Members of the genera Avicennia, Ageiceras, Aegialitis, Acanthus, Sonneratia and Laguncularia have an additional mechanism for dealing with excess salt, for they posess salt-excreting glands on the either the lower surface (e.g. Avicennia) or both lower and upper surface of their leaves (e.g. Aegicera).