Oxford University experts make squirting cucumber discovery

The team solved the long-standing mystery using a mix of experiments, high-speed videography, image analysis, and mathematical modelling.

The squirting cucumber, known scientifically as Ecballium elaterium, owes its name to its unique seed dispersal method.

When ripe, the cucumber's ovoid-shaped fruits detach from the stem and explosively eject seeds in a high-pressure jet of mucilage.

This projectile launch, which lasts only 30 milliseconds, propels the seeds to speeds of around 20 metres per second, and distances up to 250 times the length of the fruit, which is around 10 metres.

The exact mechanism of this seed dispersal, and its impact on the plant's reproductive success, had been poorly understood until now.

The fruit of the squirting cucumber (Image: Chris Thorogood) In the new study, researchers from Oxford and the University of Manchester studied Ecballium specimens grown at the Oxford Botanic Garden.

They filmed the seed dispersal with a high-speed camera, capturing up to 8,600 frames per second, measured the volume of the fruit and stem before and after dispersal, and conducted CT scans of an intact cucumber.

They also monitored the fruit with time-lapse photography in the days leading up to launch.

The team then created a suite of mathematical models to describe the mechanics of the pressurised fruit, the stem, and the ballistic trajectories of the seeds.

The study's author, Dr Chris Thorogood, deputy director and head of science at Oxford Botanic Garden, said: "For centuries people have asked how and why this extraordinary plant sends its seeds into the world in such a violent way.

"Now, as a team of biologists and mathematicians, we’ve finally begun to unravel this great botanical enigma."

The team identified the key components of the plant’s seed dispersal system, which includes a pressurised system, fluid redistribution, rapid recoil, and variable launch.

The redistribution of fluid from the fruit back into the stem is thought to be unique within the plant kingdom.

The researchers used their mathematical model to explore the consequences of altering different parameters.

They found the squirting cucumber's seed projection method has been fine-tuned to ensure near-optimal dispersal and the plant's success over generations.

Co-author Dr Derek Moulton, professor of applied mathematics at the Oxford Mathematical Institute, said: "The first time we inspected this plant in the Botanic Garden, the seed launch was so fast that we weren’t sure that it had actually happened.

"It was very exciting to dig in and uncover the mechanism of this unique plant."

Co-author Dr Finn Box believes the findings could have potential applications in bio-inspired engineering and material science, including on-demand drug delivery systems.