The Incredible Journey of Plants, Reviewed

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‘You need to imagine a plant as a huge brain’ … the plant neurobiologist Stefano Mancuso. Photograph: Alessandro Moggi

Thanks to Amy Fleming for this book review:

The secret life of plants: how they memorise, communicate, problem solve and socialise

Stefano Mancuso studies what was once considered laughable – the intelligence and behaviour of plants. His work is contentious, he says, because it calls into question the superiority of humans

9781635429916I had hoped to interview the plant neurobiologist Stefano Mancuso at his laboratory at the University of Florence. I picture it as a botanical utopia: a place where flora is respected for its awareness and intelligence; where sensitive mimosa plants can demonstrate their long memories; and where humans are invited to learn how to be a better species by observing the behaviour of our verdant fellow organisms.

But because we are both on lockdown, we Skype from our homes. Instead of meeting his clever plants, I make do with admiring a pile of cannonball-like pods from an aquatic species, on the bookshelves behind him. “They’re used for propagation,” he says. “I am always collecting seeds.”

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Flower power … Mancuso’s team has shown that Mimosa pudica can retain learned information for weeks. Photograph: Alamy

Before Mancuso’s lab started work in 2005, plant neurobiology was largely seen as a laughable concept. “We were interested in problems that were, until that moment, just related to animals, like intelligence and even behaviour,” he says. At the time, it was “almost forbidden” to talk about behaviour in plants. But “we study how plants are able to solve problems, how they memorise, how they communicate, how they have their social life and things like that”.

Mancuso and his colleagues have become experts in training plants, just like neuroscientists train lab rats. If you let a drop of water fall on a Mimosa pudica, its kneejerk response is to recoil its leaves, but, if you continue doing so, the plant will quickly cotton on that the water is harmless and stop reacting.

The plants can hold on to this knowledge for weeks, even when their living conditions, such as lighting, are changed. “That was unexpected because we were thinking about very short memories, in the range of one or two days – the average memory of insects,” says Mancuso. “To find that plants were able to memorise for two months was a surprise.” Not least because they don’t have brains.

In a plant, a single brain would be a fatal flaw because they have evolved to be lunch. “Plants use a very different strategy,” says Mancuso. “They are very good at diffusing the same function all over the body.” You can remove 90% of a plant without killing it. “You need to imagine a plant as a huge brain. Maybe not as efficient as in the case of animals, but diffused everywhere.”

One of the most controversial aspects of Mancuso’s work is the idea of plant consciousness. As we learn more about animal and plant intelligence, not to mention human intelligence, the always-contentious term consciousness has become the subject of ever more heated scientific and philosophical debate. “Let’s use another term,” Mancuso suggests. “Consciousness is a little bit tricky in both our languages. Let’s talk about awareness. Plants are perfectly aware of themselves.” A simple example is when one plant overshadows another – the shaded plant will grow faster to reach the light. But when you look into the crown of a tree, all the shoots are heavily shaded. They do not grow fast because they know that they are shaded by part of themselves. “So they have a perfect image of themselves and of the outside,” says Mancuso…

Read the whole review here.

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