In the plant world, it's really dog-eat-dog. So much so that even two peas in a pod will fight each other to survive.
The plant wars are fought largely underground.
When the roots of two plants converge, plants somehow know how to tell the competition from themselves, and they grow accordingly.
A plant's roots will grow more robustly into competing territory, while not overcrowding its own soil.
But how does a plant know the difference? Perhaps it senses chemicals, scientists have suggested.
To get to the root of the problem, researchers cleaved one common garden pea plant into two, then let the pair grow side-by-side. The plants competed as if their separated twin was an alien, even though it was genetically identical.
"This eliminated the possibility that the mechanism was based on specific chemical recognition," says Penn State researcher Omer Falik.
"The results prove that at least in the studied plants, self/non-self root discrimination is based on physiological coordination between roots belonging to the same plant," Falik said. "Such coordination might be based on internal pulsing of hormonal or electrical signals which desynchronize when the plants are separated."
Which is to say smart scientists still don't know how brainless plants pull off such a seemingly intellectual task.
Falik presented the findings yesterday at the annual meeting of the Ecological Society of America.