Determining the Effect of Raindrops Impact Location on Seed Dispersal Of Splash-Cup Plants

Splash-cup plants are unique plants that use the conical shape of their seed capsules and the kinetic energy of raindrops to disperse their seeds.  When raindrops fall into the mm-scale cup-shaped capsules the seeds are propelled out of the cup over 1 meter away from the parent plant, a distance up to ten times the height of the plant.  The dispersal of these seeds maybe important to minimize the competition between the seedlings and the parent plant.  Amador et al. used 3D printed models to show that a cup angle of 40°  and off-center drop impacts maximizes dispersal when no seeds are present in the cup. Although these findings indicated broadly that off-center raindrops were more effective, no systematic study has been conducted to examine how the precise impact location on the splash-cup plants affects seed dispersal. In this study, we used 3D printed splash-cups and high-speed video to analyze the effect on dispersal of six different drop impact locations ranging from the center to the edge of the cup.  We find results for different cup angles as well as in the presence and absence of seeds. We found that drop impact locations near the outer edge of the splash-cup yield the highest dispersal distances in some cases.