Meeting Abstract
P1.144 Monday, Jan. 4 Explosive Seed Dispersal Mechanism in Sand Bittercress (Cardamine parviflora) HAYASHI, M*; WANG, J; GERRY, S.P.; ELLERBY, D.J.; Wellesley College mhayashi@wellesley.edu
Some plants disperse their seeds ballistically using elastic energy stored in pod tissues. Species may rely solely on this mechanism or recruit an additional secondary dispersal method e.g. wind or water. Ballistic performance was quantified in Sand Bittercress (Cardamine parviflora), an herbaceous annual that uses only this seed dispersal mechanism. We hypothesized that the launch mechanism of this specialized ballistic disperser would be more effective than in a species that also used a secondary mechanism. The launch trajectories and seed dispersal pattern were quantified using a high-speed camera and a computer ballistics model. The mechanical energy storage capacity of the valves was also determined by re-extending the coiled valve tissue with an ergometer. The mean and maximum launch velocities were 6.3 ± 0.3 (mean ± SEM, n=83) and 12.0 ms-1 respectively. The mean launch angle (55.9 ± 1.4 above the horizontal, mean ± SEM, n=83), was steeper than that predicted by the ballistics computer model to maximize dispersal distance. It also differed significantly from the horizontal (0º), the expected mean launch angle for a random angle distribution. Mean and maximum dispersal distances were 0.94 ± 0.05 (mean ± SEM, n=83) and 1.85 m respectively. The mass specific energy storage capacity of the pod valves was 72.4 ±12.4 J kg-1 (mean ± SEM, n=15). The efficiency of transferring this stored energy into seed kinetic energy was 6.7%. This energy transfer efficiency was higher than that in Impatiens capensis (0.5 %), a species that relies on secondary dispersal via water flow to achieve long distance dispersal. With the mean launch distance also greater in C. parviflora than I. capensis (0.94 vs. 0.44 m), these outcomes suggest a more effective seed launching mechanism in the ballistic specialist C. parviflora.
