Frictional properties of flower stems in the plant Hippeastrum reginae (Amaryllidaceae)

Abstract

Plant flower stems covered with three-dimensional (3D) wax prevent access of ants that rob flower nectar and do not contribute to the plant cross pollination. This phenomenon, called greasy pole syndrome, is caused by the ant’s failure to gain a foothold on slippery waxy stems due to dislodged wax particles. The aim of this study was to analyze frictional properties of 3D wax projections specific to flower stems in Hippeastrum reginae by means of a microtribometer. Using the cryo scanning electron microscopy approach, we obtained images of shock-frozen plant surfaces with intact and smeared wax layers. Compared to wax-free stem samples, intact waxy stems showed significantly reduced frictional coefficient. The obtained results allowed us to provide some plausible explanations about the mechanism of the slipperiness of the 3D wax coverage on plant surfaces involved in the greasy pole syndrome. It is most probably based on easy delamination of the layered structure of single wax projections and on finally building of smearing surfaces with presumably lower intrinsic friction between individual layers. This knowledge can potentially contribute to the development of future physical control barriers based on dry lubricants with application in pest control.