PLANTA SAPIENS

Are plants sentient?

Calvo, a professor of philosophy of science at Universidad de Murcia in Spain, begins classes by demonstrating that, when exposed to an anesthetic, mimosa leaves stop withdrawing and Venus flytraps stop trapping. If a plant can be put to sleep as an animal can, writes the author, “perhaps we might consider the possibility that plants are not simple automatons or inert, photosynthetic machines. We might begin to imagine that plants have some kind of individual experience of the world. They might be aware.” To the relentlessly “zoocentric” human mind, movement and intelligence are linked, but plants could not exist in the brutal competition for survival if they did not take in information, learn, and plan ahead. Although lacking neurons like animals, they use similar electrical signals to engage with their surroundings. Despite possessing a completely different system, they’re doing something similar. Many scientists disagree with these notions, arguing that plant “behavior” is simply adaptation, a genetically encoded response to a stimulus that has proved advantageous over evolutionary time. Taking up the challenge, Calvo agrees that “it’s up to us to prove it” and proceeds to describe sophisticated behavior that will impress even skeptical readers. Following the sun during the day, some plants turn at night to face the sunrise the following day. Kept in a black box in the lab, they will not lose the memory for three or four days. Simple slime molds gather to form large masses than can solve maze problems and remember molecular likes and dislikes through communication between individual cells. Along with fascinating examples, Calvo devotes equal space to arguments with philosophers and fellow scientists over the meaning of intelligence. Readers will find it difficult to resist his claim that plants tailor their forms and experiences to their environments in a way that animals simply cannot. “If we look closely at how they do this,” writes the author, “we will be able to begin to understand why they do.”

Persuasive evidence for plant intelligence.