A new study shows that goldenrod plants exhibit a type of intelligence that defies traditional definitions of intelligence by adapting their responses to herbivores based on the presence of nearby plants and environmental cues.
By detecting the red light reflected from distant leaves, goldenrod can detect other nearby plants without even touching them. When goldenrod is eaten by herbivores, it adjusts its response depending on whether another plant is nearby. Is such a flexible and adaptive response in real time a sign of intelligence in plants?
This isn’t an easy question to answer, but chemical ecologist Andre Kessler posits plant intelligence in a recent journal article. Plant Signaling and Behavior.
Definition of intelligence in plants
“There are more than 70 published definitions of intelligence, and even within a given field there is no agreement on what intelligence is,” said Kessler, a professor in the Department of Ecology and Evolutionary Biology in the College of Agriculture and Life Sciences.
Many people believe that intelligence requires a central nervous system with electrical signals that serve as a means of processing information. Some plant biologists liken the vascular systems of plants to the central nervous system and suggest that some central unit within the plant allows them to process and respond to information. However, Kessler categorically disagrees with this idea.
“Although we clearly see electrical signals in plants, there is no strong evidence for any homology with the nervous system, but the question is, how important are these signals to the ability of plants to process environmental signals?” said.
To defend plant intelligence, Kessler and co-author Michael Mueller, a postdoctoral researcher in his lab, narrowed their definition down to its simplest elements: “The ability to solve problems based on information you receive from the environment, directed at a specific goal,” Kessler said.
As an example, Kessler cites his previous research on goldenrod and its response to being eaten by pests. When leaf miner larvae eat goldenrod leaves, the plant secretes a chemical that signals to the insect that the plant is damaged and the food source is poor. These airborne chemicals, called volatile organic compounds (VOCs), are also taken up by nearby goldenrod plants, encouraging them to mount their own defenses against insect larvae. In this way, scrofula spreads the damage by carrying herbivores to its neighbors.
Experiments and observations
In a 2022 journal article plants Kessler and co-author Oleksandr Chauta, Ph.D. ’21 conducted experiments to show that the goldenrod plant can also detect high amounts of far-red light reflected from the leaves of neighboring plants. When there are neighbors around and the goldenrods are eaten by insects, they become more invested in tolerance to herbivores, growing faster, but they also begin to produce defensive compounds that help plants fight off harmful insects. Without neighbors, plants do not grow as quickly when eaten, and chemical responses to herbivores differ significantly, but they still tolerate fairly large numbers of herbivores.
“This fits our definition of intelligence,” Kessler said. “Depending on the information it receives from the environment, the facility changes its default behavior.”
Neighboring goldenrod also shows intelligence when it detects VOCs that indicate the presence of a pest. “Volatile emissions from a neighbor are a harbinger of future herbivory,” Kessler said. “They can use the environment to predict a future situation and act accordingly.”
Applying the concept of intelligence to plants could inspire new hypotheses about the mechanisms and functions of chemical communication in plants and change the way people think about what intelligence really means, Kessler said.
The second idea is timely, as artificial intelligence is a hot topic of interest. For example, according to him, artificial intelligence does not solve the problem of achieving the goal, at least for now. “AI is not even smart by our definition of intelligence,” he said. Instead, it relies on patterns it detects in the information it can access.
The idea that intrigued Kessler stemmed from mathematicians in the 1920s who suggested that plants were perhaps more like beehives. In this case, each cell works like a separate bee and the entire plant resembles a beehive.
“This means that the plant brain is the entire plant, without the need for central coordination,” Kessler said.
The superorganism has chemical signals instead of electrical signals. Studies by other researchers have shown that each plant cell has a broad light-sensing spectrum and sensor molecules to detect very specific volatile compounds from nearby plants.
“They can smell the environment very clearly; “As far as we know, every cell can do this,” he said. Cells may be specialized, but they all sense the same things and communicate using chemical signals to trigger a collective response in growth or metabolism. “The idea is very appealing to me,” he said.
Source: Port Altele
