The Squirting Cucumber

Plants have gone to great lengths when it comes to seed dispersal. One of the most bizarre examples of this can be found in an ambling Mediterranean plant affectionately referred to as the squirting cucumber. As funny as this may sound, the name could not be more appropriate. 

Known scientifically as Ecballium elaterium, the squirting cucumber can be found growing along roadsides and other so-called "waste places" from the Mediterranean regions of western Europe and northern Africa all the way to parts of temperate Asia. It is the only member of its genus, which resides in the family Cucurbitaceae. It is a rather toxic species as well, with all parts of the plant producing a suite of chemicals called cucurbitacins. In total, it seems like a rather unassuming plant. It goes through the motions of growing and flowering throughout the summer months but the real show begins once its odd fruits have ripened. 

A cursory inspection would not reveal anything readily different about its fruit. Following fertilization, they gradually swell into modest sized version of the sorts you expect from this family of plants. It's what is going on within the fruit that is rather interesting. As the fruit reaches maturity, the tissues surrounding the seeds begin to break down. The breakdown of this material creates a lot of mucilaginous liquid, causing internal pressure to build. And I mean a lot of pressure. Measurements have revealed that at peak ripening, pressures within the fruit can reach upwards of 27 atm, which is 27 times the amount of atmospheric pressure we experience when standing at sea level!

A cross section of the fruit showing the weakened connection point.

A cross section of the fruit showing the weakened connection point.

At the same time, the attachment point of the stem or "peduncle" begins to weaken. With all that pressure building, it isn't long before something has to give. This is exactly the moment when the squirting cucumber earns its name. The stem breaks away from the fruit, revealing a small hole. Within a fraction of a second, all of that pressurized mucilage comes rocketing outward carrying the precious cargo of seeds with it. 

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The result is pretty remarkable. Seeds are launched anywhere from 6 to 20 feet (1 - 6 m) away from the parent plant. This form of dispersal falls under the category of ballistic seed dispersal and it is incredibly effective. Getting away from the competitive environment immediately surrounding your parents is the first step in the success of any plant. The squirting cucumber does just that. It is no wonder then that this is an incredibly successful plant species. 

Photo Credits: [1] [2] [3]

Further Reading: [1] [2] [3]