There is a plant that lives in the Mediterranean basin, apparently harmless, which hides one of the most explosive and ingenious strategies in the plant world. It is called spray cucumber (Ecballium elaterium), and became the subject of a fascinating study that revealed all the details of its seed dispersal mechanism through a real explosion.
A team from the University of Kiel, Germany, presented research at the Society for Experimental Biology Annual Conference in Antwerp, revealing how this plant not only ejects seeds with surprising force, but does so by aiming with precision, adjusting the launch angle before expulsion. A jaw-dropping discovery — and not just because of the spectacular nature of the explosion.
Why does this plant explode?
Nature teaches: being too close to the “parents” is not always an advantage. Plants that drop seeds at the foot of the stem risk competing with themselves for water, light and nutrients. So, some of them evolved to shoot the seeds as far as possible.
This is precisely the case with the spray cucumber. When its fruit, rich in water, reaches maturity, it transforms into a natural pressure chamber. In an instant, the explosion ejects a gelatinous mass containing up to 30 seeds, which are fired at speeds exceeding 47 km/h. A mechanism as efficient as it is delicate. Everything must happen at the right time, without compromising the integrity of the mother plant, as Helen Gorges, doctoral student and author of the study, explains:
Dispersion must be effective but controlled. Several factors must cooperate perfectly so as not to explode the fruit too soon.
A random explosion? Far from it. The researchers found that in the final days of ripening, the small stem of the fruit — called the peduncle — changes shape, slowly straightening until it reaches an inclination of 53° from the horizontal.
It is no coincidence: according to calculations, the ideal angle to maximize the shooting distance is 50°, considering height from the ground, mass of the seeds and air resistance. In practice, the plant adjusts its trajectory like an archer before shooting.
To reach these conclusions, the team combined 3D microcomputed tomography with high-speed filming at 10,000 fps, managing to capture what is impossible to see with the naked eye:
The explosions happen in a few milliseconds, but by slowing everything down we could see every detail.
Seeds that fly like bullets and “glue” the future to the ground
The video shows the seeds always coming out of the same end, all oriented with the tip forward. A strategy that reduces air resistance and prevents seeds from colliding with each other during launch.
Once landed, other evolutionary wonders come into play: the external covering of the seed, in fact, releases a mucilaginous gel which, when drying, becomes sticky like a natural glue. This helps the seeds stick to the soil, preventing them from being blown away by wind or rain. Furthermore, the gel retains humidity, promoting germination even in the arid and stony soils where the plant grows.
By analyzing the fruit’s internal tissues with micro-CT, the researchers found that the squirting cucumber accumulates water and stiffens its cell walls, turning into a small “hydraulic accumulator.” When the pressure exceeds the tissue resistance limit, the fruit splits at the weakest point, near the peduncle, releasing all the energy in a fraction of a second.
A mechanism as precise as it is powerful, made possible by an extraordinary mix of biomechanics, hydraulic pressure and adaptive strategies.
From nature to technology
What science has discovered does not stop at the plant world. Cucumber spray mechanisms are already inspiring soft robotics and medical controlled-release systems.
The concept of elastic energy stored in a gel is the same one underlying hydrogel actuators for microsurgery or ultra-localized drug delivery systems. And that’s not all: self-separating materials and self-sealing coatings are a potential basis for new biocompatible and sustainable devices, as Gorges points out:
There are many possible applications in the medical and technological fields. From soft robotics to drug delivery devices: we are learning a lot from plants.
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