Thigmomorphogenesis in Climbing Epipremnum aureum, Monsters obliqua expilata and Philodendron scandens (Araceae)

Abstract

Plants of Epipremnum aureum (Linden and André) Bunt., Monstera obliqua expilata ( M.Leichtlinii Hort.) and Philodendron scandens (C. Koch and H. Sello) were grown upright either hung by the tip or climbing on a support. Hung plants were regarded as mechanically unstimulated (control) plants; climbing plants were regarded as subjected to continous mechanical stimulation (contact of the aerial roots and stem with the support). The morphogenic alterations induced in climbing plants were: (a) In stems: The classical response pattern to mechanical stimuli, i.e., decreased elongation with concomitant increased radial growth, was observed in climbing E. aureum only; internodes of climbing M. obliqua showed an increased radial growth without changes in elongation, whereas internodes of climbing P. scandens were of similar length and diameter as those in hanging plants. (b) In aerial roots: These were very well developed in climbing plants of all three species, but grew little in hanging P. scandens , and remained undeveloped in hanging E. aureum and hanging M. obliqua . (c) In leaves: Leaf area increased in climbing plants of all three species and was significantly larger when compared with leaves of the respective hanging control plants. The results suggest that plants of the Araceae display thigmomorphogenetic responses induced by the contact of aerial roots and stems with the adjacent surface of the support.