Plant Memories

Europeans citizens and their settlers have long treated the natural world as mere ‘stuff’ that can be manipulated to achieve our human-centric ends. It wasn’t that long ago that animals were regarded as dumb beasts without the ability to genuinely feel pain or have thoughts or memories. It turns out that our presumptions of plants are similarly undergoing radical reevaluations by some in the scientific community.

After training the plants, Gagliano withheld the light. When she next turned on the fans, she had switched them to the opposite branch of the Y shape. She wanted to see if the plants had learned to associate airflow with light, or its absence, strongly enough to react to the breeze, even if it was coming from a different direction, with no light as a signal. It worked. The plants that had been trained to associate the two stimuli grew toward the fan; the plants that had been taught to separate them grew away from the airflow.

“In that context, memory is actually not the interesting bit—of course you have memory, otherwise you wouldn’t be able to do the trick,” she says. “Memory is part of the learning process. But—who is doing the learning? What is actually happening? Who is it that is actually making the association between fan and light?”

It’s telling that Gagliano uses the word “who,” which many people would be unlikely to apply to plants. Even though they’re alive, we tend to think of plants as objects rather than dynamic, breathing, growing beings. We see them as mechanistic things that react to simple stimuli. But to some extent, that’s true of every type of life on Earth. Everything that lives is a bundle of chemicals and electrical signals in dialogue with the environment in which it exists. A memory, such as of the heat of summer on last year’s beach vacation, is a biochemical marker registered from a set of external inputs. A plant’s epigenetic memory, of the cold of winter months, on a fundamental level, is not so different.

It’s absolutely amazing to learn how much we do not know, and similarly striking that so many people actively work to prevent scientists from learning more about the natural world.