Even without a central nervous system, some life forms on planet Earth can act seemingly intelligently. Plants aren’t usually thought of as sentient beings, but perhaps that’s our own brain bias. In a fascinating and controversial new paper, Cornell University chemical ecologist André Kessler and his doctoral student Michael Muller argue that the behavior of some plants may fit some definitions of intelligence.

Two scientists explain that when faced with a problem, some plant species are able to move and react to their environment using a type of memory combined with the ability to make decisions. A recent discovery in Kessler’s laboratory is an excellent example. A grass-like flower known as tall goldenrod (Solidago altissima), can apparently “hear the screams” of his neighbors being attacked by a hungry herbivore.

When leaf-eating larvae begin munching on goldenrod leaves, the plants release volatile organic compounds (VOCs) that signal to the insects that the plant is damaged and that they should move on to a better food source. Attacked plants also change the way they reflect red light emitted from their leaves, which can be seen by other plants from a distance.

Both the light and the chemicals emitted serve as specific distant warnings of impending danger to other goldenrods in the environment. Only close relatives with the proper “understanding” can crack the code embedded in the VOC. In turn, these neighboring goldenrods strengthen their defenses against predators, grow faster and produce defensive compounds similar to an animal’s immune system to fight off insects.

Kessler and Müller argue that through this silent and covert method, ancient ancestors not only integrated information from their environment, but also anticipated and prepared for future conditions based on their current environment.

Similar behavior is seen in the tobacco plant, and according to Kessler and Muller, it falls under the “umbrella of the general concept of intelligence”: achieving goals such as survival in a wide variety of environments.

Goldfish may not have nerves that communicate using electrical signals, but their cells are wired into systems that work using chemical signals, allowing the network as a whole to act and respond even if there is no central nervous system.

“They can smell their environment very clearly; As far as we know, every cell can do this,” says Kessler.

Kessler and Muller argue that a plant’s response to VOCs is more than just a reflex or a fixed pattern of action. This is a “weighted” change in behavior based on the cost of herbivory and competition with peers.

A goldenrod that is attacked when there are no other flowers around does not emit the same light from its leaves, according to a 2022 study by Kessler and his colleague Alexander Chaut.

“Depending on the information it receives from the environment, the plant changes its default behavior,” explains Kessler.

“Given this definition and the accumulating evidence, the question is not whether plants exhibit intelligent behavior, but how they achieve this without a nervous system, and what ecological consequences such behavior leads to,” Kessler and Muller note.

The attribution of terms such as “intelligence” to the plant world is highly controversial, but after decades of scientific rejection and disdain, this field of research is finally beginning to flourish.

jeweler — is hardly the only facility known to use VOCs to privately “talk” to neighbors about common threats. Scientists have known since the 1980s that some plants exchange information in this way. But most of these studies have been conducted only in the laboratory, and there is still much to learn about how plants respond to these specialized communication networks.

Some scientists are skeptical about such results and whether they can be explained in terms of a subjective language like intelligence.

But regardless of whether researchers agree on what definitions to use or which plants would meet these thresholds, it is clear that more studies are needed to test potential perception, learning, decision-making, and memory processes in our planet’s flora. The study was published on: Facility Signaling and Behavior.