Not Only Can Plants Learn, But They Remember Things Weeks Later, Fern Study Suggests
Can plants learn? A new study into Mimosa pudica ("the sensitive plant") suggests that it is indeed possible. The fern has a built-in mechanism that causes its leaves to curl up in defense, but when University of Western Australia researchers dropped water on the leaves under a variety of conditions, they found that the plant learned to stop curling its leaves in response to the harmless water.
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"[T]he defensive leaf-folding behavior in response to repeated physical disturbance exhibits clear habituation, suggesting some elementary form of learning," the researchers write. "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."
In the study, researchers led by biologist Monica Gagliano used a specially designed device to drop water on the ferns' leaves in both high- and low-light environments. After only a few seconds, plants realized that the water was safe and stopped curling up their leaves in response to the water dropper. (Watch the video below to see how the leaves defensively curl in response to a human's touch.) Incredibly, the plants seemed to remember that they learned that the water was harmless. The researchers re-tested the plants weeks later, in different environments, and the ferns still refrained from curling their leaves in response to the water.
So how do the plants remember? The researchers aren't sure, but they suspect it might have something to do with the plants' calcium-based signally network in their cells. This network works similarly to animals' memory processes, leading the researchers to wonder if the line between plant and animal is a bit fuzzier than previously thought. If plants can learn and form some sort of crude memories, what does it mean?
In a similarly amazing study published in June, researches found that plants are capable of "doing math." The plant Arabidopsis was observed strategically conserving and using starch overnight, making sure its reserve lasted until dawn. "They're actually doing maths in a simple, chemical way--that's amazing, it astonished us as scientists to see that," said the study's lead author.
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