Podostemaceae Depend on Sticky Biofilms with Respect to Attachment to Rocks in Waterfalls

Investigations of the method by which the plant body of Podostemaceae fastens to naked rocks in waterfalls refute the hitherto accepted existence of a special glue secreted by these plants. Instead, roots and crusts of Podostemaceae utilize bacteria, mainly cyanobacteria of biofilms, for attachment. These plants essentially depend on the sticky components (extracellular polymeric substances [EPS]) of slime‐coated cyanobacteria that live within biofilms covering the rocky substratum: the EPS of biofilm functions as the pasting agent. Adhesive hairs, developing from the lower side of the Podostemonad plant body, stick to the cyanobacteria threads and the biofilm matrix, which, in turn, fasten to the substratum. This mode, occurring widely, is exemplified herein with five Old World species of both subfamilies of Podostemaceae.