Meeting Abstract
Ballistochoric plants project seeds away from the parent plant so that offspring can avoid competition for nutrients and sunlight. Their diversity of seed shapes and sizes reflect the many mechanisms used for ballistic seed ejection. If the driving factor for these mechanisms is the dispersal distance, then plants with larger seeds would require more robust mechanisms to effectively disseminate their seeds. Species in the witch hazel genus Hamamelis launch seeds that are large (average of 0.04 g, sample size 33 seeds) when compared to seeds from most ballistochoric plants (seeds of similar, previously studied systems range from 10-4 g to 10-2 g). The explosive dispersal of witch hazel seeds has yet to be fully resolved, due to their extremely fast and brief movement. Now, through high speed videography, we elucidated these transient events. We collected seed capsules from four Hamamelis plants on Duke’s campus and extracted from their seed capsules the endocarps containing the seeds. We firmly secured each endocarp to the base of a desiccation chamber and recorded with a high speed camera (100,000 fps). The seeds were ejected with an average maximum velocity of 8.8 m/s and an average maximum acceleration of 120,000 m/s2 (sample size of 33 seeds, from 4 plants). Through our velocity calculations and an estimate of drag, we expect that the seeds can travel 5 m from their host plant. Endocarps with greater mass launched seeds with greater kinetic energy and maximum velocity. Hamamelis, which disperses seeds that are almost half the mass of the mechanism used to expel them (seed mass to endocarp mass ratio of 0.43), can provide insight into how the mass of the seed influences its dispersal mechanism.
