noun, plural: pneumatophores
(zoology) The air sac or float in certain siphonophores
In botany, pneumatophores are a type of aerial root. Aerial roots are roots that grow from above the ground and absorb water directly from the air. Pneumatophores are formed by certain plant species submerged in water, in waterlogged soil, or in strongly compacted soil. They emerge from the typical roots and then stick up out of the soil. The root surface of the pneumatophores is covered with lenticels, i.e. raised pores allowing gas exchange between the atmosphere and the internal tissues. The lenticels take up air into the spongy tissue of the pneumatophore. The oxygen is then spread throughout the plant. Examples of plant species that form pneumatophores are the black mangrove and the grey mangrove. These mangrove plants form pneumatophores since the saline soil is anaerobic and therefore hampers the submerged roots to carry out gas exchange through the soil.
In zoology, a pneumatophore is one of the three major body parts in a colony of siphonophores. The other two body parts are the nectosome and the syphosome. The pneumatophore serves as an air sac or float that aids the colony to stay afloat at the proper level in the ocean. It is located at the top of the colony.
Word origin: pneumat- ("air" or "gas") + -phore ("bearer")