Plant Intelligence: The Evidence That Plants Are Conscious

Plant intelligence is a difficult concept to accept, as it implies a new way of looking at intelligence. Tony Trewavas has written an article called Plant Intelligence: A Overview. It provides examples and explanations of the plant’s physiological complexity that Trewavas describes as intelligence. “Intelligence” is defined as: “(a] is the ability of an individual to interact with its environment (or environments), (b) is related the agent’s capability to succeed in some goal or target, and (c), depends upon how adaptable they are to different environments. Flexible behavior is an important factor in intelligence. Accordingly, to Trewavas, the more adaptable an organism is to different environments and objectives, the higher the level of intelligence.

Flexibility is what I want to concentrate on because it is a crucial aspect of intelligence. If properly demonstrated in plants, it can also undermine other explanations of plants’ behavior. Flexible behavior, in my view, requires active thinking to challenge physical mechanisms. However, it allows the organism’s natural instincts to adapt to new situations and to use logic to do so. Because of the high likelihood that plants have active thought and are able to exhibit flexible behavior, I’d like to show how some plants’ physical systems and structures can be understood as flexible behavior. In this article, the Scientific Inference of Other Minds by Robert Pargetter, I will explain why it’s logically possible that we believe in plant intelligence. Then I will offer scientific examples of plants’ flexible behavior. He states that his theory on inference to best explanation states that a hypothesis should be considered the best evidence that is available at the time.

Pargetter basically believes that if the hypothesis is the best explanation for a situation, it makes sense to believe in its accuracy. This theory would be useful to determine whether plant behavior can be best explained by rationalization.

Scientists know that plant systems are extremely complex and sophisticated. A plant’s root cover is one of its most complex parts. Trewvas describes one root cap in his article on Arabidopsis’ root cap. It covers the root tip and is made up of around 200 cells. It is dynamic. The cap is made of a layer that connects to the root meridtem. The cap cells gradually push outward. They are sloughed when they reach the cap’s surface. But they are capable of sensing and assessing a variety signals throughout their life. The structure of the cap is similar to the one in the nervous system and cell above. It has both a core as well as a periphery. This structure seems to be the basis for intelligent behavior. The cap can sense a wide variety of signals, which may help to build resilience.

Root caps are able to adapt to their environment by moving in the right direction and shedding dead cells. However, this could be explained as a simple mechanistic process that has been triggered by chemical reactions. The root cap attracts to survival needs and grows toward them. If it cannot sense survival needs, the root cap stops growing toward them. Active thought that causes flexible behavior in a way that is against a physiological mechanism is simply an excuse.

Another reason for plants not being flexible is that they lack neurons. This means that the plant does not have the ability to perform cognitive activity. But, as there is no universal system that can support cognition, the absence of one does not mean that cognition is gone. In his article Cephalopods & the Evolution of the Mind Peter Godfrey Smith describes the neural differences between cephalopods, and yet maintains that they possess intelligence and flexible behavior (Godfrey Smith 5). “Cephalopods are a completely different organization in both body and brain,” he writes (Godfrey Smith 5). While the vertebrate plan has a head, spinal cord, and peripheral nervous system, cephalopods have a “different organization” (Godfrey-Smith 5).

“Ladderlike’ nervous systems” were composed of neurons that were packed together in front of the eyes. Many ganglia were also fused. The invertebrate’s neural plan was submerged, but it was only partial” (Godfrey Smith 5). He also mentioned that “a common Octopus has approximately 500 million neurons.”

Two-thirds of them aren’t in the brain at any time, but in arms,” which means that “their nervous systems remain much more ‘distributed’, more spread throughout the body than ours (meaning human),” (Godfrey Smith 5). He also gives an example of cephalopod flexibility. He wrote,

“A group in Indonesia was shocked to discover that octopus were carrying half-coconut shells around as portable shelters. 2009). As it walked on the sea floor, the octopus would place one half-shell in the other. The octopus then would assemble the half-shells into a circle and climb inside. While many animals use found items as shelters, such as hermit crabs, it’s rare to be able to disassemble and assemble a tool like this.

While cephalopods are known for their flexible behavior, they also seem to have an active mind that responds spontaneously and logically to changing situations. It is impossible to explain the complex behavior of coconut Octopuses as a physical mechanism. Pargetter’s theory suggests that they are intelligent and this would be the only explanation.

Although the brain and neural structures of cephalopods are completely different from those of humans, it is believed that cephalopods exhibit intelligence due to their flexible behavior. This shows that intelligence and cognition are not universal. Therefore, it is not necessarily a problem that plants lack a brain or neural structure. It is possible that their thinking process has not been discovered. It was only recently that humans discovered that some of the closest evolutionary relatives, like chimpanzees and octopuses, could think or have intelligence. Peter Godfrey Smith’s article explains that we now have to consider the existence of other animal species, like cuttlefish and octopuses. We will be able to discover new intelligence by studying and researching the biology of plants.

We have found that cephalopod behavior can be explained by defining it as flexible, which is intelligence. If we accept that cognition is not a universal system, then there is no need for a brain or neural network. Flexible is the best explanation. Here is where things get tricky. Many plant systems are activated by physical processes, which can be explained without the need for intelligence. Flexible behavior in plants has been the subject of very little research. Even experiments have not produced definitive results. Tony Trewavas concludes his article with the title “Games that plants play.” This section contains unique aspects of plant biology and I believe it presents examples of plants exhibiting flexible behavior.

Tony Trewavas closes his article by discussing a legume’s game of “prisoner’s dilemma”, in which it plays with rhizobia bacterium. This simple explanation of the interactions between the plant and bacteria is that certain rhizobia bacteria can convert dinitrogen from the atmosphere into organic nitrogen by the process of nitrogen fixation. There are several types of Rhizobia bacteria. However, only certain types can fix dinitrogen into Organic Nitrogen. The plant will then form “nodules” around the rhizobiabacteria, which can fix or ignore other bacteria. This eliminates any potential ‘free-riders. Trewavas briefly addresses this behavior. But, Ellen L. Simms and D. Lee Taylor provide additional information regarding the synbiotic relationship between legumes and Rhizobia bacteria in their article Partner Choice in Nitrogen Fixation Mutualisms of Legumes and Rhizobia (Sims Taylor 369).

Simms & Taylor describe the initial need for organic nitrogen. They explain that, although “Nitrogen has an extremely high abundance, about 79% in the atmosphere,” it remains “dinitrogen,” and plants “cannot convert it… to useful organic form” (Simms; Taylor 370).

This is why nitrogen fixation has become an essential part of legume survival. This makes it necessary for them to have a symbiotic relationship. The legumes supply the rhizobia with carbohydrates. The legume traps the nitrogen fixating bacteria and ignores the non-fixating bacteria. Both organisms benefit from the relationship. They both receive essential nutrients. This relationship is flexible, but it’s not clear if it is.

Peter Godfrey Smith gave the example of the coconut-octopus hiding in coconut halves because it was intelligent and flexible. It also makes use of objects found in its surroundings to help it survive. It removes the rhizobia bacterium that can be a nuisance and encapsulates it to protect the nitrogen-fixing bacteria. It is using an environment tool to get organic nitrogen in order to survive. Active thought would be considered flexible behavior. It must also make quick, rational choices about which bacteria it will keep and discard. This behavior can be explained by flexibility, which is a part of intelligence. This behavior requires that the legume reject some rhizobia bacterias and accept other ones. To continue to fix dinitrogen into organic nitrogen in its nodule, the legume will also sacrifice some of its carbohydrates. This is also a complex behavior that requires active thought. This is more than a physical mechanism. It sacrifices some of its survival benefits for another organism. And what this other organism can do to the legume. These three steps are complex because they involve using bacteria from the environment for survival, determining between non-nitrogen fixation and nitrogen fixation rhizobia bacterial, and then sacrificing a portion carbohydrate to feed and entice rhizobia bacterium to stay. This complex behavior cannot be described as a mechanical one.

Because plants are flexible, I believe they can think and reason logically as well as spontaneously react to their environment. A lack of a brain or neural structure would render plants ineligible for universal cognition. We will continue to learn more about plant biology and see more evidence for flexible behavior. It is possible for plants to exhibit flexibility and have thought. This would increase intelligence around the globe. This will require humanity to redefine intelligence, cognition. The world will be much larger.


  • jamielane

    Jamie Lane is a 31-year-old blogger and traveler who loves to share his educational experiences with others. He is a graduate of the University of Michigan and has been traveling the world ever since. Jamie is always looking for new and interesting ways to learn, and he loves to share her findings with others.

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