That lovely smell of freshly cut grass is probably very enjoyable for you and most people, but for the grass it’s a cry for help and a chemical warning to other plants in the vicinity.
Plants cannot move or run away when they are in danger, so they use other methods of defense. They have an arsenal of molecular responses, which are used in various circumstances. For example, when plants are attacked by an insect, they can poison it by activating certain compounds, they can release certain chemicals that will attract the insect that eats the assailant and they can warn other plants of the danger by releasing airborne chemical signals or through their underground network. Depending on the species of the plant and its genetic code, the methods and chemicals in the process can be different.
We know that plants can communicate, but can they feel pain? Although numerous researches suggest so, most scientists are baffled by the idea that there could be a sensation of pain without the brain or at least some kind of primitive nervous system.
Scientist from Bonn, Germany have preformed a study to see if they could acoustically measure the stress levels of plants while being hurt, using specially devised laser-powered microphone. When you cut off a leaf or a stem of a plant or if it’s affected by some disease, the plant releases ethylene gas over its entire surface. In a controlled environment, scientists gathered the ethylene using a complex device and bombarded it with specially calibrated lasers. As a result, molecules of ethylene vibrate emitting a sound wave which is picked up over a microphone. Bigger the stress, louder the signal. Picking up these cries for help can be very useful in agriculture for early detection of diseases and pests and for proper fruit storage.
Researchers of the University of Missouri-Columbia discovered that plants even respond to sounds of being eaten. Recording the sound of caterpillar eating a leaf and playing it to plants raised their defense when they were actually attacked.
Daniel Chamovitz, dean of Life Sciences at Tel Aviv University, wrote a book “What a Plant Knows” in which he explores similarities in the way plants and humans experience the world. A very descriptive example he uses is a plant Mimosa pudica, known for closing her leaves when being touched. Giving that it has such an obvious reaction, it was the perfect plant for the experiments. Research team tried multiple methods to test if plants feel similar to humans and other living beings. For example, they used certain anesthetics like chloroform and methoxyflurane to see if they have the same effect on the mimosa. Result was astounding – mimosa didn’t react to touch after being exposed to the anesthetics. If you apply an electric shock to your hand for example, it will twitch. Same thing goes for mimosa – putting electrodes on it and sending an electrical charge across the leaf caused the mimosa to close.
“What a Plant Knows” also describes how plants distinguish between light and different colors, how they are aware of gravity and certain aromas. From simplest to most complex plants, there is a world of rich and varied sensory inputs.
One of the most revolutionary books on the subject of plant senses is probably “The Secret Life of Plants” (1973) written by Peter Tompkins and Christopher Bird. Although heavily criticized by scientists for pseudoscientific claims, this book gives some fascinating ideas about the life and emotions of plants. The book reveals many unusual phenomena, including plant sentience, shown through various experiments. One of them included the experiment of Cleve Backster, who worked as an interrogation specialist for the CIA. In 1966 Backster had impulsively put electrodes of a lie detector on a leaf of his dracaena plant to see how it will be affected by certain stimuli. When he poured water onto the roots, the plant gave a reading similar to a person experiencing a small emotional stimulus. This accidental discovery led Cleve Backster to immerse himself in this subject, study deeper and perform more experiments. As a result of his research a theory of “primary perception” came out, claiming that plants have extrasensory perception (ESP). We know that Mythbusters did an experiment where they exhibited how different genres of music, bad words and nice words can affect plants. But Backster went few steps further, proposing that plants do not only react to vibrations of sound, but also to thoughts.
The criticism that “The Secret Life of Plants” faced was a result of “outrageous” ideas displayed in the book. If the principles of plant life and their communication with the environment shown in the book are true, it would totally change not just our idea of plants, but life in general.