Animation shows how a drop of water triggers the dandelion seed's morphing motion, to close the pappus (parachute-like structure). Credit: Dr Maddy Seale.
The dandelions – famous for their fluffy seed carrying parachutes, provide food for birds and pollinator insects, including bees. They are also known for their impressive capability to extend habitats.
The dandelion seeds are some of the best flyers in nature, fabled to travel more than 100 kilometres, without an energy input. What makes them such a great flyer? It turned out that they can tune their flight depending on the weather conditions.
The dandelion seed is carried by a parachute like umbrella called pappus, which are made of about 100 bristles. The pappus catch the wind, enhance air drag and carry the seed. It closes in rainy or foggy weather, when the wind is weak. In drier, more windy conditions, dandelions widen the pappus to better catch the wind so the seeds can fly freely.
However, until now how they detect the weather conditions and tune their flight was a mystery.
Now an international team including Edinburgh researchers has uncovered the engineering working behind the tuning of dandelion dispersal.
Their work, published in Nature Communications, found the seed-carrying pappus open and close using a hinge-like structure like no other known before.
The centre of the pappus swells absorbs water and change their shape, changing the angle of the attachment of the bristles and closing the pappus. This is completely reversible, and the pappus opens when the air is dry again.
The hinge at the centre of the pappus has a unique radial, tube-like design to orchestrate the movement of 100 bristles. The different parts of the tube swells to different degree when wet, which was the key to enable the shape change of the pappus.
Dr Naomi Nakayama who started this work at the University of Edinburgh says: “Our findings reveal how the dandelion makes perhaps the most important decision in a plant’s life – to stay or go seek a better habitat.”
There were many unique technical challenges. “We developed bespoke methodology and models, and we had to dissect and image a tiny structure that had rarely been studied before as well as decide which features to focus on for modelling. These were fascinating challenges requiring frequent discussion and iteration of experiments and simulations,” the lead author Dr Maddy Seale explains.
Dr Ignazio Maria Viola (School of Engineering, University of Edinburgh) collaborated with researchers from the universities of Oxford, Lyon, Imperial College London and École Polytechnique de Paris, to bring together their diverse expertise in plant biology and mechanical engineering.
Dandelions are important foundation of urban and rural ecosystems, and knowing the sensitivity of their dispersal to the environment helps us predict how the changing climate will impact ecology. This work may also inspire new environmental sensors and actuators in soft robotics or animated materials engineering.
Find out more
- Read “Dandelion pappus morphing is actuated by radially patterned material swelling” by Madeleine Seale, Annamaria Kiss, Simone Bovio, Ignazio Maria Viola, Enrico Mastropaolo, Arezki Boudaoud & Naomi Nakayama, published May 2022 in Nature Communications.
- Watch: How do dandelions sense and respond to their environment so well?