Effect of Salinity on Seed Buoyancy and Germination in Pochote (Pachira quinata: Malvaceae), a Tropical Wind-Dispersed Tree

Pochote, Pachira quinata is a tropical tree species found in lowland areas on the coast of Costa Rica.  Seeds are dispersed by wind when a dry capsule opens, releasing seeds covered with kapok fibers.  These diaspores, or seeds with their kapok threads attached, are held aloft and float from the parent tree on currents of air.

This study was performed to explore the potential for secondary dispersal, via water, in pochote, and in particular to determine: (i) the length of time pochote seeds could remain afloat in sea water, in brackish water, and in fresh water and (ii) whether the amount of time spent in each of those media affects the ability of pochote seeds to germinate.

All water was collected from either the San Miguel River or coast water at San Miguel Biological Reserve in Costa Rica. Trials were performed outdoor in plastic basins.

Germination of pochote seeds immersed in fresh water reached around 40% after 6 days of observation. While seeds were unable to germinate in sea water, immersion in fresh water after this period led to germination rates equal to those of seeds that had been immersed in fresh water alone. Trials with brackish water yielded similar results.

The results of this study confirm the potential for secondary dispersal by fresh water for pochote, and confirm the possibility of secondary dispersal in sea water.  Further studies are needed to determine the maximum length of time pochote seeds immersed in sea water will remain viable.