Meeting Abstract

P3-12   -   Mesh-like Surface Features of Castilleja Seeds Increase Aerodynamic Drag Zimmerman, H*; Small, BM; Walro, DF; Astley, H; University of Akron; University of Akron; University of Akron; University of Akron hlz2@uakron.edu

Dispersal of offspring is crucial for reducing resource competition, reducing inbreeding depression, and increasing the spread of the species. While the offspring of many animal species disperse via active locomotion, plants mostly rely on external forces to disperse seeds, one of the most common being wind. Wind dispersal is a successful strategy used in a wide variety of plant lineages that have each evolved unique means to harness air flow to their advantage. As the production of these reproductive units is energy-intensive, plants are pressured to maximize favorable dispersal, usually by maximizing the aerodynamic drag of the seed and thereby reducing falling speed. Well-known examples of wind dispersal include winged or plumed seeds such as maple seeds and dandelions. A less-examined mechanism is found in disparate “dust-seed” plants such as orchids and Indian paintbrushes (Castilleja), in which honeycomb-like mesh exteriors surround tiny seeds. This surface morphology has evolved convergently in several plant lineages, suggesting it has a function in wind dispersal. To test the function of this morphological feature, we used 3D printed models in a Reynold’s number matched system. We recorded video of the seeds falling in still air to ascertain the relevant Reynold’s number. We then created models with and without the presence of the mesh to drop in water, with model size selected such that the realistic model had similar Reynolds numbers to the natural seeds. Preliminary trials with these models show that the honeycomb-mesh reduced the seed’s fall speed by 57%. By utilizing micro-CT scanning and 3D printing technologies, we can directly test the function of the seed morphology, even in species for which manipulative tests have previously been infeasible due to their small seed size.