The leading edge of spinning hornbeam and maple seeds provides lift by generating a tornado-like vortex.

References

Journal article
Leading-Edge Vortices Elevate Lift of Autorotating Plant SeedsScienceNovember 6, 2009
D. Lentink, W. B. Dickson, J. L. van Leeuwen, M. H. Dickinson

“The twirling seeds of maple trees spin like miniature helicopters as they fall to the ground. Because the seeds descend slowly as they swirl, they can be carried aloft by the wind and dispersed over great distances. Just how the seeds manage to fall so slowly, however, has mystified scientists…The research, led by David Lentink, an assistant professor at Wageningen, and Michael H. Dickinson, the Zarem Professor of Bioengineering at Caltech, revealed that, by swirling, maple seeds generate a tornado-like vortex that sits atop the front leading edge of the seeds as they spin slowly to the ground. This leading-edge vortex lowers the air pressure over the upper surface of the maple seed, effectively sucking the wing upward to oppose gravity, giving it a boost. The vortex doubles the lift generated by the seeds compared to nonswirling seeds.” (Caltech Media Relations 2009)

[Video showing vortices can be downloaded from http://mr.caltech.edu/assets/619-mapleseed.mp4.]

Book
Maple seeds and animals exploit the same trick to fly

Organism
Japanese MapleAcer palmatumSpecies