Breathing through your roots?

Mangrove is a type of forest in the tropics and subtropics, located along a low coast or a river, which is submerged at high tide, is sheltered and muddy, has a salty soil and is characterized by a vegetation consisting of trees and shrubs with breathing roots or aerial roots.

Mangrove has adapted to special nutritional circumstances. Between reef and beach where the surf is less ferocious, coral rubble and sludge will settle down. Because of the lower surf there is less oxygen. In such an environment mangrove trees often grow. They have rhododendron lookalike leaves and aerial root systems of all kinds to breathe air, since they cannot do so in the mud. 

There are large intercellular spaces in the outer layers of the stilt or breathing roots of mangroves and other aquatic plants. They serve to provide the plants with oxygen.