Life in the Current: Anatomy and Morphology ofUtricularia neottioides

Rheophytism is extremely rare in theUtriculariagenus (there are four strictly rheophytic species out of a total of about 260).Utricularia neottioidesis an aquatic rheophytic species exclusively growing attached to bedrocks in the South American streams.Utricularia neottioideswas considered to be trap-free by some authors, suggesting that it had given up carnivory due to its specific habitat. Our aim was to compare the anatomy of rheophyticU. neottioideswith an aquaticUtriculariaspecies with a typical linear monomorphic shoot from the sectionUtricularia,U. reflexa, which grows in standing or very slowly streaming African waters. Additionally, we compared the immunodetection of cell wall components of both species. Light microscopy, histochemistry, scanning, and transmission electron microscopy were used to address our aims. InU. neottioides, two organ systems can be distinguished: organs (stolons, inflorescence stalk) which possess sclerenchyma and are thus resistant to water currents, and organs without sclerenchyma (leaf-like shoots), which are submissive to the water streaming/movement. Due to life in the turbulent habitat,U. neottioidesevolved specific characters including an anchor system with stolons, which have asymmetric structures, sclerenchyma and they form adhesive trichomes on the ventral side. This anchor stolon system performs additional multiple functions including photosynthesis, nutrient storage, vegetative reproduction. In contrast with typical aquaticUtriculariaspecies from the sectionUtriculariagrowing in standing waters,U. neottioidesstems have a well-developed sclerenchyma system lacking large gas spaces. Plants produce numerous traps, so they should still be treated as a fully carnivorous plant.