Do Plants Have Memory?

Most of us see plants as passive organisms: they don't move, they don't run, and they don't retaliate when you put them under the chainsaw. 

Of course, plants do move. You can find plenty of timelapse videos of flower blossoming and twigs moving on youtube, and some plants can even act fast enough to capture insects.
Similar to animals, plants react when stimulants around them change: the availability of sunlight, nutrient, and water. However, we normally don't perceive plants to be capable of memorizing things and .... learn, or behave, right?

And that's because plants do not have memory, they do not possess brains, right?

Well, according to a paper published last year by Monica Gagliano, associate professor of biology at the University of Western Australia, it seems that some plants can not only remember what happened to it, but also store that memory for up to a month.

Mimosa pudica. Image: wikipedia.org

Ladies and gentlemen, I present to you, Mimosa pudica, or commonly known as the sensitive plant. As its name implies, the plant folds its leaves into what seems like a defensive curl whenever something touches it. It's so sensitive that even a sense of falling could also prompt the plant to fold its leaves.

Gagliano wondered if she repeatedly stimulate the plants in the same manner, would the plants eventually realize that nothing terrible was going to happen and thus stopped folding their leaves?

So she loaded several pots of Mimosa pudica onto a special plant-dropping device using a sliding steel rail and dropped roughly six inches, not once, but 60 times with a 5-second interval. The plants would land onto a foam that prevented bouncing. The speed of the fall, however, was sufficient to stimulate the plant into folding their leaves.
At first.

Gagliano soon observed that some plants did not close their leaves fully when dropped. As the experiment progressed, they began to close less and less - which means the plants were changing their behavior - until finally, the leaves were completely left open even when dropped.

However, there could be other reasons why the plants stopped folding their leaves. One of the possible reasons is energy. Folding leaves is work, and after 60 repeated falls some of the plants simply got tired and stopped folding their leaves.
But Gagliano then took some of these "exhausted" plants and placed them in a shaker, shook them, and immediately they curled up their leaves again.

A week later, she repeated the same dropping experiment, and again the leaves failed to fold. This was repeated week after week, and 28 days later the plants still "remember" to not to fold their leaves when dropped.

So does this mean that plants actually have brains?

Well, Gagliano's experiment proved that some plants do remember. But no, they don't have brains. Gagliano herself wrote that plants may lack brains, but they do possess a sophisticated signaling network, which could function more or less like a brain, albeit radically different in design and structure.

Malcolm