How Dandelions 'Decide' to Spread Their Seeds

Every kid loves dandelions. Blow on the puffy white head and seeds fly everywhere.

Dandelion seeds can travel for miles before finally floating down and settling somewhere new.

But without the help of children, the seeds still waft away and researchers recently discovered how the plants decide to spread.

Each seed is tethered to about 100 bristles and combined, those make a parachute-like top to help the seeds move. When the seeds come unattached from the head of the flower, the parachute bristles catch a ride on the wind, carrying the seeds away.

“We noticed that the dandelion parachute is closed in foggy mornings but then open again when the sun is up during the day,” study author Naomi Nakayama of the department of bioengineering at Imperial College London, tells Treehugger.

“We studied how the dandelion fly (and found a previously unknown mode of flight). And then we wanted to know how this reversible closure of the parachute affects the flight. After that, we couldn’t help looking into how exactly this morphing is controlled. (We are biomechanics researchers.)”

This hairy parachute closes when the air is humid, which often means the wind is weak. In drier, more windy conditions, dandelions widen their parachutes to better catch the wind so the seeds can fly freely.

“The dandelion uses a bundle of hairs (what the parachute-like structure really is) to enhance air drag and aid its flight. There are many small seeds that fly this way, so the dandelion is not that unique in this aspect, but it is certainly an iconic example,” says Nakayama.

“Unlike insects or birds, they don’t need any energy input to fly a long distance—even hundred of kilometers—they simply catch the wind.”

In their new research, scientists have found the “decisions” that the plants make when determining how to disperse their seeds.

How They Open and Close

Researchers uncovered the parachutes open and close using what they say is like an actuator, a device that converts energy and signals into motion. But this actuator doesn’t use any energy.

The middle of the dandelion’s parachute is able to sense the amount of humidity by absorbing water molecules in the air. Using signals about humidity information, they either open their parachutes and fly off or they close them and stay where they are.

“The center of the parachute changes its shape, moving the bristles altogether in unison,” Nakayama says. “It's basically a sponge made of no-longer living plant cells, which are arranged in a tube with an empty cavity inside. The inner side and the outer side swell with water to different degrees, and that drives the movement.”

The results were published in the journal Nature Communications.

Climate Change and Soft Robots

Knowing what triggers dandelions to spread their seeds could help scientists learn how they deal with climate change. They say understanding the response could help researchers design new soft robots, which are those made from flexible materials that mimic soft bodies.

“How plants move their body parts are different from animals and a simple, localized expansion could be enough to move arms,” Nakayama says. “Movement of a few arms has been achieved, but this is the first of many arm actuators. It is simple in design, so there is a lot of scope for biomimicry.”

But understanding how dandelions work is also fascinating because of the key role the plant plays in the environment.

“The dandelion is the foundation of ecosystems. It feeds the insects and birds—bees feed on it more than any other species,” Nakayama says. “So, the environmental sensitivity of their flight is an important topic for us to understand how nature will change in the future climates.”