Wind-dispersed plants have evolved ingenious ways to lift their seeds. The common dandelion (Taraxacum officinale) uses a bundle of drag-enhancing bristles that helps to keep their seeds aloft. A new study, led by University of Edinburgh researchers Ignazio Maria Viola and Naomi Nakayama, shows that movement of air around and within the dandelion’s parachute-shaped bundle enables seeds to travel great distances.
“We carried out experiments to better understand why dandelion seeds fly so well, despite their parachute structure being largely made up of empty space,” Dr. Viola, Dr. Nakayama and their colleagues said.
“Our study revealed that a ring-shaped air bubble forms as air moves through the bristles, enhancing the drag that slows each seed’s descent to the ground.”
This form of air bubble — named the separated vortex ring — is physically detached from the bristles and is stabilized by air flowing through it.
The amount of air flowing through, which is critical for keeping the bubble stable and directly above the seed in flight, is precisely controlled by the spacing of the bristles.
This flight mechanism of the bristly parachute underpins the seeds’ steady flight.
It is four times more efficient than what is possible with conventional parachute design.
“The dandelion’s porous parachute might inspire the development of small-scale drones that require little or no power consumption,” the study authors said.
“Such drones could be useful for remote sensing or air pollution monitoring.”
“Taking a closer look at the ingenious structures in nature — like the dandelion’s parachute — can reveal novel insights,” said study first author Dr. Cathal Cummins, also from the University of Edinburgh.
“We found a natural solution for flight that minimizes the material and energy costs, which can be applied to engineering of sustainable technology.”
The findings appear in the October 18, 2018 issue of the journal Nature.
Cathal Cummins et al. 2018. A separated vortex ring underlies the flight of the dandelion. Nature 562: 414-418; doi: 10.1038/s41586-018-0604-2