pneumatophore
1. An aerial negatively geotropic root that acts as an organ of gaseous exchange. Pneumatophores are produced by mangroves and other plants that grow in waterlogged oxygen-deficient soils. See mangrove swamp.

2. The gas-filled float of certain colonial cnidarians of the class Hydrozoa, such as Physalis (Portuguese man-of-war).

pneumatophore Specialized ‘breathing’ root developed in some plant species that grow in waterlogged or strongly compacted soils, e.g. mangroves. The aerial part of the root contains many pores, enabling gas exchange with the atmosphere. Internally, a well developed system of intercellular spaces allows gases to diffuse throughout the submerged portion of the roots.

pneumatophore A specialized ‘breathing’ root developed in some plant species that grow in waterlogged or strongly compacted soils (e.g. mangroves). The aerial part of the root contains many pores through which gases are exchanged with the atmosphere and from which they diffuse by means of intercellular spaces throughout the submerged portion of the root.