By using the same experimental framework normally applied to test learnt behavioral responses in animals, biologists from Australia and Italy have successfully demonstrated that Mimosa pudica – an exotic herb native to South America and Central America – can learn and remember just as well as it would be expected of animals.
Mimosa pudica is known as the Sensitive plant or a touch-me-not. Dr Monica Gagliano from the University of Western Australia and her colleagues designed their experiments as if Mimosa was indeed an animal.
They trained Mimosa‘s short- and long-term memories under both high and low-light environments by repeatedly dropping water on them using a custom-designed apparatus.
The scientists show how Mimosa plants stopped closing their leaves when they learnt that the repeated disturbance had no real damaging consequence.
The plants were able to acquire the learnt behavior in a matter of seconds and as in animals, learning was faster in less favorable environment.
Most remarkably, these plants were able to remember what had been learned for several weeks, even after environmental conditions had changed.
“Astonishingly, Mimosa can display the learned response even when left undisturbed in a more favorable environment for a month. This relatively long-lasting learned behavioral change as a result of previous experience matches the persistence of habituation effects observed in many animals,” the biologists wrote in a paper published online in the journal Oecologia.
“Plants may lack brains and neural tissues but they do possess a sophisticated calcium-based signaling network in their cells similar to animals’ memory processes,” they explained.
The biologists concede that they do not yet understand the biological basis for this learning mechanism, nevertheless their set of experiments has major implications – not least, it radically changes the way we perceive plants and the boundaries between plants and animals, including our definition of learning as a property special to organisms with a nervous system.
Gagliano M et al. 2014. Experience teaches plants to learn faster and forget slower in environments where it matters. Oecologia, published online January 05, 2014; doi: 10.1007/s00442-013-2873-7