New Study Cracks Squirting Cucumber Seed Explosion Mystery

The mystery surrounding the exact way the squirting cucumber disperses its seeds and how it impacts its ability to reproduce remained a subject of intrigue for centuries. But now, in a new study, researchers from the Universities of Manchester and Oxford carried out a number of tests on Ecballium specimens and solved the ballistic mystery behind the squirting phenomenon, reported CNN. 

Their findings, published Monday in the journal Proceedings of the National Academy of Sciences, explained that these inedible cucumbers (Ecballium elaterium, which means "throw out" non-Greek) build up fluid in their fruit and eventually explode due to internal pressure. The fluid that drains from the fruits into the stem changes its form and propels the cucumbers away so they vomit their contents. 

“It is a new idea that optimal seed dispersal is not only about building the greatest pressure in the fruit,” said Dr. Angela Hay, a research group leader at the Max Planck Institute for Plant Breeding Research in Cologne, Germany.

According to the study, the best seed launch depends on balancing pressure from fluid buildup with other unique changes that prepare the fruit for eruptive action.

When ripe, the fruits separate from the stalk and release the seeds in a high-pressure mucilage jet. The seeds reach speeds of around 20 meters per second during this 30-millisecond projectile launch, and they land up to 250 times the fruit's length (about 10 meters).

The experiment involved using a high-speed camera to record the seed dispersal (up to 8600 frames per second), measuring the volume of the fruit and stems both before and after the dispersal and doing CT scans and indentation tests on an intact cucumber. The study also used time-lapse photography to track the fruit in the days before launch. After that, they created a number of mathematical models to explain the ballistic trajectories of the seeds, the stem, and the mechanics of the compressed fruit.

“The explosive launch of the cucumber plant has evolved over generations to help it survive. The way that the stem is able to re-position itself to the perfect angle and build enough pressure to maximize spread has been key to helping regulate the plant's population. These mechanisms allow the plant to disperse seeds over a wide area and reduce overcrowding and competition among offspring and other neighbouring plants, ensuring a better chance of survival for the next generation,” said lead researcher Finn Box from The University of Manchester.