Plants and the Memories We Never Knew They Could Have

On a basic level, plants are demonstrating the ability to think and remember. For them, it might not be about survival of the fittest, but the smartest.
Source: Sten Porse / Wikimedia

Mimosa pudica. It’s a name that sounds like it belongs attached to a mixed gelatinous alcoholic beverage, not a plant that has researchers discussing whether or not one of our leafy counterparts in the vegetable kingdom might have the ability to remember what has happened to it in the past.

So, this isn’t about a bubbly champagne and orange juice party favorite, but another casual (albeit firmly rooted in a pot of dirt with no ability to speak) observer judging how lousy a tipper some people can be after being served their boozy mimosa?

Before Monica Gagliano, an evolutionary ecologist at the University of Western Australia, even began her study into M. pudica this creeping perennial herb had an established reputation for responding to physical contact. It’s why gardeners refer to it as the ‘sensitive’ or ‘touch-me-not’ plant — its leaves fold inwards as a defensive reaction to the lightest caress.

Source: University of Western Australia

Obviously, the Mimosa pudica does not have a brain, so where does all this talk of having memories come into play? Gagliano decided to study why this particular plant’s leaves always seemed to assume a defensive position when touched. She selected 56 specimens and with the help of a specially designed measured vertical rail began gently dropping them six inches to a padded landing zone.

As she expected, the plants followed their usual playbook and folded their leaves up.

These handful of drops gave Gagliano a base from which to work from. She then began submitting her specimens to repeated drops at five-second intervals, 60 drops in total. She duplicated the process another six times over the course of one day, and as the number of drops increased the physical reactions by her test subjects decreased. Their leaves remained outward, almost like a person stretching their arms skyward while enjoying a rollercoaster.

Was this proof of the plants adapting to the scenario, or were they just exhausted from having the proverbial rug pulled out from under them hundreds of times? Gagliano took a sample of tested specimens and gave them all a good shake to check their reaction to this new form of startling stimuli. Leaves curled up.

The basic concept of plants potentially possessing traits that might make an individual wonder if they could be sentient beings is not a new one. 1973’s “The Secret Life of Plants” detailed experiments based around an eclectic mix of grounded plant science with some oddball approaches involving bananas and onions being hooked up to a polygraph machine. Gagliano bypassed subjecting her plants to lie detector tests, but instead repeated her experiment every week for a month. It was a “been there, done that” scenario for the plants – drop after drop, their leaves remained open.

Gagliano’s findings have raised the ire of some members of the scientific community who simply don’t believe plants have the necessary genetic make-up to form memories. For centuries scientists have said that plants don’t think, they only do what they’ve been genetically programmed to do. After all, it’s that inherited infrastructure that makes up for plants not having a brain. Gagliano had this to say this in her published paper on her study:

“…the process of remembering may not require the conventional neural networks and pathways of animals; brains and neurons are just one possible, undeniably sophisticated, solution, but they may not be a necessary requirement for learning.”

As it turns out, M. pudica might not care if you are, in fact, a cheapskate when it comes to tipping. But it has presented a possibility that has scientists and researchers talking to one another about approaching our way of assessing plant behaviour differently – maybe over a champagne mimosa or two.