Endohydrophily

Endohydrophily is a form of pollination by water in aquatic plants in which the transfer of pollen and fertilization occur inside the reproductive organs rather than being mediated by pollen moving across the surface of the water. The term is used in some botanical literature to distinguish an underwater, intra-floral pathway from the more common surface or external water pollination.

Endohydrophily is part of the broader category hydrophily, which includes mechanisms where water serves as the medium for pollen movement. Within hydrophily, endohydrophily is contrasted with epihydrophily (surface-level pollen transfer on or near the water surface) and hypohydrophily (underwater pollen transfer involving pollen grains moving to stigmas in the water column). Endohydrophily, by some definitions, describes pollination that proceeds entirely within submerged floral structures, with pollen grains germinating and pollen tubes growing through the style to fertilize ovules, aided by water flow that remains within the plant’s own tissues.

Ecological and evolutionary considerations: Endohydrophily is reported in a small minority of aquatic angiosperms and is more likely to occur in species with highly specialized floral architecture that protects pollen from dilution or loss in open water. The term is not universally adopted, and some authors treat endohydrophily as a descriptive extension of underwater pollination rather than a separate mechanism.

Because of variable usage, readers should consult specific taxonomic treatments to determine how a given source defines endohydrophily in relation to other forms of hydrophily.