New research shows that Goldenrod plants exhibit a form of intelligence by adjusting their responses to herbivorous animals through the recognition of neighboring plants and environmental signals. This challenges traditional definitions of intelligence within the scientific community.
The Goldenrod species can identify other nearby plants without physical contact, by sensing the ratio of red light reflected from the leaves. When Goldenrod plants are attacked by herbivores, they adjust their response based on the proximity of other plants. Is this real-time, adaptive, and flexible response a sign of intelligence in plants?
This question is not easy to answer, but Professor Andre Kessler has made a case for plant intelligence in a recent paper published in the journal Plant Signaling and Behavior.
Identifying Intelligence in Plants
Plants may possess intelligence.
Kessler is a Professor in the Department of Ecology and Evolutionary Biology at the College of Agricultural and Life Sciences in Germany. He states, “There are over 70 published definitions of intelligence, and there is no consensus on what it is, even within a specific field.”
Many believe that intelligence requires a central nervous system, with electrical signals serving as the means for processing information. Some botanists equate the vascular system in plants with a central nervous system and propose that there exists a centralized entity in plants that allows them to process and respond to information. However, Professor Kessler firmly disagrees with this view.
He says, “While we clearly see electrical signals in plants, there is no substantial evidence showing any similarity to the nervous system (in animals). The question is, how important are these signals for the ability of plants to process environmental information?”
To argue for plant intelligence, Kessler and co-author Michael Mueller have narrowed their definition down to the most fundamental elements. Professor Kessler refers to it as “the ability to solve problems, based on information received from the environment to achieve a specific goal.”
As a case study, Kessler points to his previous research on Goldenrod and its response when attacked by pests. When the larvae of leaf-eating beetles consume Goldenrod leaves, the plant emits a chemical to inform insects that it is unhealthy and a poor nutritional source. It’s akin to showing a “poverty card” when confronted by robbers to avoid danger. In this way, Goldenrod lures herbivores to nearby plants for feeding.
The chemicals released into the air by Goldenrod, known as volatile organic compounds (VOCs), are also absorbed by neighboring Goldenrod plants, prompting them to create their own defense mechanisms against the beetle larvae.
Experiments and Observations
In a 2022 paper published in the journal Plants, Kessler and co-author Alexander Chautá conducted experiments demonstrating that Goldenrod can sense higher ratios of red light reflected from nearby plants from a distance. When neighboring plants are present and the Goldenrod is being eaten, they invest more in producing chemicals to attract herbivores to adjacent plants. When no neighboring plants are present, Goldenrod does not employ that strategy.
Kessler states, “This aligns with our definition of intelligence. Depending on the information received from the environment, plants will change their behavior.”
Nearby Goldenrod also demonstrates intelligence when they detect VOCs signaling the presence of pests. Kessler explains, “The amount of volatile emissions from the surroundings is a predictive sign of future herbivores. They can recognize environmental signals to anticipate future situations and then act based on the signals received.”
Professor Kessler notes that applying the concept of intelligence to plants could inspire new hypotheses about the mechanisms and functions of chemical signaling in plants, while also shifting human perceptions of the true meaning of intelligence.
This second idea is quite timely as artificial intelligence is currently a hot topic. Professor Kessler gives the example that artificial intelligence does not solve problems aimed at a goal, at least not at this moment. He states, “Artificial intelligence, according to our definition of intelligence, doesn’t even possess a shred of intelligence.” Instead, artificial intelligence merely processes based on patterns it identifies in available information.
An idea that intrigues Professor Kessler comes from mathematicians in the 1920s, who suggested that plants might operate more like a beehive mechanism. In this mechanism, each cell functions like an individual bee, and the entire plant resembles a beehive. Professor Kessler emphasizes, “This means that the brain of the plant is the entire plant without a coordinating center.”
Instead of transmitting electrical signals, there are chemical signals throughout the plant. Some studies by other scientists have shown that every plant cell can recognize a wide spectrum of light and possesses sensory elements to detect very specific volatile compounds from neighboring plants.”
Professor Kessler asserts, “They can very accurately sniff out their surrounding environment. As far as we know, every cell can do this. Cells may be specialized, but they also recognize similar things, and they communicate through chemical signals to trigger collective responses during growth or metabolism. That idea is very appealing to me.”
