Meeting Abstract

P1.111  Thursday, Jan. 3  Explosive dispersal and self-burial in seeds of the filaree, Erodium cicutarium (Geraniaceae) EVANGELISTA, D*; DUMAIS, J; HOTTON, S; University of California, Berkeley; Harvard University; Harvard University devangel@berkeley.edu

The filaree (Erodium cicutarium), a small, invasive, flowering plant related to geraniums, performs two noteworthy biomechanical tricks with its seeds: (1) the plant can fling its seeds a half meter; and (2) the seeds can bury themselves by drilling into the ground, twisting and untwisting five to ten full turns in about 15 minutes. These are accomplished using awns, helical bristles of hygroscopically-active dead tissue attached to the seeds. Here, we report our observations on the self-burying process. Without any muscles, the seed can self-bury by differential swelling of awn tissue in response to daily variations in humidity. Self-burial was observed using time-lapse video of awns and environmental SEM of sections of awn tissue. Based on the observations, we developed a simple mechanical model that accounts for the coiling behavior of the awn and allows comparison of the strain energy stored before dispersal with dispersal distances reported in other literature. The mechanics of seed dispersal and self-burial help understand the invasive potential of this species and suggest future work using the mechanical model to examine evolutionary tradeoffs in the morphology of seed dispersal mechanisms among other species within the Geraniaceae.