Science: Plant sensitivity, back in the spotlight

Turning towards the sun to catch the light, searching for a fence to climb, vibrating to the rhythm of the wind - plants have their own sensitivity, different from that of humans, but just as complex in its silent way. In recent years, this "vegetal intelligence" has become a major research topic, bringing back to mind an intuition that is over a century old: plants feel the world, informs AFP. "What we mean here by sensitivity is not that plants have emotions like humans, but that they receive information from their environment in a precise, continuous and dynamic manner, and this information triggers reactions visible or not to the human eye," explains Delphine Arbelet-Bonnin, a doctor in cell biology and co-author, with Lucia Sylvain Bonfanti, of the volume Sensibles par nature, published in early October by Ulmer Publishing.

• An old idea, confirmed by modern science

From Charles Darwin to Claude Bernard, the idea that plants actively react to stimuli is not new. What has changed is the depth of observation: contemporary biology allows us to see and measure how plants perceive, process and respond to their environment. Capturing messages from the air, touching without skin, communicating through roots or responding to sound vibrations - all these plant behaviors define a form of non-neuronal perception. How do plants "feel”? Although they lack a nervous system, plants have sensors located in the membranes of their cells, where they transform the information received from the environment into electrical signals. A spectacular example is Drosera tokaiensis, a carnivorous plant with purple flowers, which "feels” the approach of a caterpillar. At that moment, electrical impulses run through the entire plant - signals similar to neural ones - while phytohormones transmit the information throughout the body. The result? The petals quickly close, protecting the reproductive organs from insect invasion. "The signals are not identical to those of the animal nervous system, but they are very close. They generate diffuse biochemical reactions that control growth and metabolism,” explains Arbelet-Bonnin.

• Examples of plant sensitivity

From the sunflower, which follows the light, to the ivy and beans, which cling to grow, or the spectacular Alsomitra macrocarpa, whose parachute seeds can glide for meters, the plant world is full of subtle movements and strategies. But despite these achievements, humans often remain "blind” to plant life. The American botanist James Wandersee called this phenomenon plant blindness back in 1986: our tendency to ignore beings that do not move or make noise.

• A change of perspective

"Researchers have been turning their gaze towards plants for about 20 years,” observes Lucia Sylvain Bonfanti, who is preparing an interdisciplinary thesis on plant sensitivity, at the confluence of psychology, neuroscience and geography. She speaks of a "plant revolution” in the human and social sciences: a growing interest in how plants communicate, coordinate, act. Not only biology, but also anthropology, geography, philosophy and art are beginning to rediscover the silent world of plants. "We see this change in literature, in theatre, in poetry. Plants are once again becoming a presence, a partner in existence, not just a decoration,” says Bonfanti. A study conducted in the UK shows that, after periods of isolation, people's interest in gardens and plants has increased considerably. "Plants are associated with well-being, with tranquility, with the idea of a return to nature. Perhaps we are learning to look at them again," concludes Delphine Arbelet-Bonnin. In a world of speed and noise, the sensitivity of plants reminds us that perception does not mean haste, but attention.