How the intelligence of the trees is measured and what it means for maintaining our life on earth

Plants are sentient beings which have emotions, who feel the pain when damaged, enjoy Mozart, can respond to unspoken thoughts of humans and more. Cleve Backster, a former intelligence agent, best known for his experiments with plants using a polygraph (lie detector) instrument in the 1960s long before science has discovered the intelligence of plants capable of cognition, learning, memory and communication. He hooked up the galvanometer of the polygraph instrument to his house plant and to his astonishment, he found that simply by imagining the plant being set on fire, the needle of the galvanometer rose, recording a rush of electrical activity which showed that the plant was distressed. He claimed that plants “feel pain” and they have “primary perception.” After having repeated the experiment with other plants, he found that plants reacted to the good and ill thoughts of the people near. Stunningly he further discovered that a plant which had witnessed the murder or destruction of another plant could pick up the murderer among the line of suspects causing a record of significantly heightened levels of electrical activity when the destroyer came close.

Years later, Stefano Mancuso, the renowned plant and cell neurobiologist and his colleagues proved that plants have 15-20 distinct senses including sight –their perception of different wavelengths of light, touch –through the roots, sound and smell –through the vibrations and chemicals in the air and in the earth. His experiments conducted at the International Laboratory of Plant Neurobiology at the University of Florence, showed that plant roots would seek and find a buried water pipe through which water flew, suggesting that plants do hear the sound of water.  Through their extensive sensory capacities, the plants gather the information from the environment and “decide” on how to respond. On the choice and intention of the plants, the phenomenal bean plant experiment shows the conscious effort of the young bean plant striving to reach the pole to climb and grow. Once it reaches its goal, on touching the pole, the strenuous extension and clenching form of the leaves are relaxed and an air of opening up with confidence permeates the stalk and the leaves. He stated :

If plants are conscious, then yes, they feel the pain, which allows them to survive when in danger. They communicate complex information via smell, taste and electrical impulses in their silent but sophisticated language.

Beeches, spruce and oaks feel the pain when a caterpillar starts nibbling on them discovered the German forester, Peter Wohlleben. The tissue on the leaf where it is damaged due to nibbling is changed and electrical signals are transmitted so that the chemicals are produced and sent to the leaves to avert the caterpillar from its meal. Another astonishing finding of is the behavior of the acacia trees in Africa, when eaten by the giraffes, they emanated ethylene gas that put off the giraffes and which signaled the neighboring trees of the same species and forewarned them to pump toxin into their leaves. Wohlleben concludes that trees have the sociality feature, enabling them to interact with one another and with the rest of the ecosystem and even to other species. Their sessile life style as plant biologists term it, enables them with an extensive apprehension of the environment in which they have to find everything they need and at the same time defend themselves as beings rooted to the ground.

In Mancuso’s view, our tendency to equate behavior with mobility causes to underestimate what plants can do and their intelligence.  “A plant has a modular design, it can lose up to ninety percent of its body without being killed,” he says. There is nothing like that in the animal world. It naturally creates resilience.” Devoted to his work with plants, Mancuso believes that we should treat plants with respect, protect them from destruction and avoid genetic manipulations against their nature. This approach does not prevent us from eating them. “Plants evolved to be eaten,” he claims, “for it is part of their evolutionary strategy, supported by their modular structure and replaceable organs.”

Comparing the intelligence of plants and humans, Mancuso emphasizes the plants’ capacity to choose, learn and remember as we do. He puts forth that we all exist on a continuum on which intelligence is a property of life.

I agree that humans are special. We are the first species able to argue about what intelligence is… the ability to comprehend and solve problems. People grant intelligence to computers more than they do to plants because artificial intelligence is our creation and reflects our intelligence back to us. It depends on us unlike plants do. If we were to vanish tomorrow, plants would be just fine but imagine if the plants were to vanish… Our dependence on plants reminds us of our own weakness.

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We must stop regarding plants as passive and mute objects of our world. It is human arrogance and the fact that the lives of plants unfold on a much slower time scale than ours keeps us from appreciating their intelligence.

Duygu Bruce