SCIENCE
01/27/2016 05:10 pm ET

This Plant Lets Loose A Stinky Defense Mechanism When Humans Touch It

Inanimate objects don't seem to trigger the same response.
The leaves of the Mimosa pudica, whose roots emit a wasteful smell.
State University of New York at Albany
The leaves of the Mimosa pudica, whose roots emit a wasteful smell.

Scientists discovered that a plant known for releasing a sulfuric smell somehow differentiates between a menacing human hand and some inanimate objects before emitting the pungent odor. 

The tropical, flowering Mimosa pudica makes a stink like a bodily function when its roots are disturbed. It's the vegetational version of an animal's fight or flight response to danger, according the research published recently in Plant Physiology

The plant releases a foul scent when a person comes in contact with its roots or rips the plant from the ground, but a touch from wood, glass or metal trigger no such response, according to the article. It was written by a group of researchers, including Rabi Musah, a chemist at State University of New York at Albany. 

"It’s pretty amazing that the roots of a plant would be able to distinguish between different forms of matter in such a way as to respond to a human finger on one hand, but not respond to objects made of glass or metal on the other hand," said Musah in a statement

The compounds produced by the plant include sulfur dioxide, methylsulfinic acid, pyruvic acid, lactic acid and thioformaldehyde, researchers found. They conducted tests by monitoring the air around specimens in petri dishes after exposing them to different conditions. 

The question, of course, is why the plant reacts the way it does to different materials. Musah has found microscopic protuberance on the roots that appears associated with the emissions, and said she hopes her future research will find an explanation for the phenomenon. 

The M. pudica has other distinguishing characteristics that are more satisfying to behold. It's is also known as the sensitive plant or touch-me-not, among other names, because its leaves rapidly move when prodded.

Other plant species are infamous for their strong smells too, but unlike the sensitive plant, but they emit their aroma from above-ground sections. 

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