Brilliant Green: Plant Intelligence Explained

Words by
Georgina Reid
Images by
Georgina Reid
| December 7, 2016

Plants are intelligent. They communicate, sleep, remember, and even manipulate. Why, then, do we treat them as little more than objects to be used (and abused) at our whim? This question forms the premise of Brilliant Green, a book by Italian plant neurobiologist Stefano Mancuso and Alssandra Viola. It’s a passionate argument for the acknowledgement of the importance, intelligence, and rights of plants.

For many thousands of years humans have dismissed the brilliance of plants. The roots of this ambivalence, Mancuso suggests, lie in the stories told by monotheistic religions, and centuries of western philosophical and scientific thought. “In holy scripture the plant world not only isn’t considered equal to the animal world, it isn’t considered at all,” Mancuso asserts.

Aristotle, in On the Soul, classifies plants as only-just-living things because they have the capacity for nourishment and reproduction, but don’t have a soul. “Two characteristic marks have above all others been recognised as distinguishing that which has soul, and that which has not – movement and sensation” (On the Soul).

Mancuso soon clearly proves that plants do move and feel, and the majority of the book is dedicated to exploring the incredible ways plants interact with the world around them.

Another reason Mancuso provides for our dismissal of the plant world is psychological. “Our relationship with plants is one of absolute, primordial dependence,” he writes. Mancuso likens the relationship to that of teenage-hood. Remember that time when you pretended you didn’t need your parents? That you could function very well without their input, thank you very much? But you knew in your heart you couldn’t?

“No one likes depending on another,” he writes. “Dependence coincides with a position of weakness and vulnerability that we don’t enjoy contemplating… we’re so dependent on plants that we do everything everything we can not to think about them.” It’s an interesting thought to ponder – that our avoidance of feelings of weakness drives us ignore our absolute dependence on plants. At our own peril, I’d suggest.

Following his exploration of the historical and cultural basis of our ideas about plants, Mancuso proceeds to methodically pull them apart, backing up his argument with science. He explores the way plants and their cells are built, the time frames they operate within, the way they communicate, their senses, and intelligence.

Banksia coccinea
Banksia coccinea

One very obvious way plants and animals differ is in movement. Plants can’t move in the ways we can – there’s no running from predators when you’ve got roots. Instead of throwing their branches in the air and giving up, they’ve just went ahead and built themselves so that no one part is truly indispensable.

When you think about it, this is pretty amazing. If my head gets chopped off, that’s it. I’m gone. Pfft. A plant, on the other hand, would just grow a new one, and likely relish the challenge.

Then there’s communication. Plants communicate both internally and externally with having to utter a word!

The roots of a plant will tell the leaves (via both electrical and chemical/hormonal signals) to shut the door if the soil is dry and the leaves are losing water through transpiration. Or, they’ll tell competitors to bugger off, protecting their territory through colonising the soil with their root systems. But only if they’re not family…

Yep, plants can also identify their own kin. Amazing, huh? Mancuso writes of a study in 2007 which consisted of growing 30 seeds from the same plant in one pot, and in a second identical pot 30 seeds from different plants. “The thirty plants from different mothers behaved as expected, developing a greater number of roots in an attempt to dominate the territory and assure themselves sufficient food and water, to the disadvantage of the other plants,” He writes.

The thirty plants from the same mother, however, behaved quite differently. They produced far fewer roots, advantaging the plant’s aerial growth. “What was observed was non-competitive activity linked to their genetic proximity,” writes Mancuso.

The plant, it turns out, checks out a potential rival before attacking or defending, and if it discovers a genetic affinity, instead of competing it chooses to cooperate.”

Mancuso also writes of how certain plant species, when under attack from insects will, after identifying the insect, use chemical warfare to make their leaves taste terrible, or even poisonous to the animal. The production of these substances occur only in the leaves being attacked and their neighbours, not the whole plant. Amazing!

Eucalpytus something (I can't remember the species!)
Eucalpytus something (I can't remember the species!)

I could ramble on for days about how phenomenal plants are, and how Brilliant Green really is brilliant in both its passion and delivery of seriously interesting information. But I won’t. All I’ll say is this: Read it. You’ll never look at plants in the same way again.

I’ll just throw one more bit of brilliance in. Because, really, this is what it’s all about:

“Clearly the plant kingdom is not only an essential ingredient of life on our planet, but a great gift to human beings and to our intelligence – a gift we often heedlessly throw away. It’s been estimated that human beings know scarcely 5 – 10 percent of the plant species present on Earth, and from them we derive 95 percent of all our most important medicines. Each year, thousands of species we know nothing about become extinct, and untold gifts to humanity are lost with them. Perhaps knowing that plants perceive, communicate, remember, learn, and solve problems will help us someday to see them as closer to us and will also offer us the opportunity to study and protect them more effectively.”

Thank you, Stefano Mancuso. You’re my hero.

Brilliant Green: The Surprising History and Science of Plant Intelligence is published by Island Press, and is available to buy here.

The images accompanying this story are from a 2014 trip to Western Australia. The indigenous plants of WA are incredible. If you really want to blow your mind, I’d suggest reading Brilliant Green in the middle of the bush in the south west of WA in the middle of wildflower season.

Featured image is of Hakea victoria – one of the weirdest plants I’ve ever seen.

Regelia velutina
Regelia velutina

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