Plants could one day force us to change our definition of intelligence
Some may be reluctant to think that plants made of roots, stems and leaves may have intelligence or consciousness. But scientists have been debating this idea for decades.
A recent document tried to draw a final line on this issue by rejecting it completely. She argued that the essential physical characteristics found in conscious animals are absent from plants. All these species have an information processing network composed of nerve cells arranged in complex hierarchies that converge in a brain. Plants, on the other hand, have no nerve cells at all, let alone a brain.
But what would happen if assuming that any intelligence must resemble ours would limit what we could discover about how plants actually work? Plants may have very different physical systems from ours, but they react to their environment and use a sophisticated signaling network to coordinate how all the different parts of the plant work together. This even extends to other organisms with which plants cooperate, such as fungi. There is even an argument that such a system could lead to a form of consciousness.
It has long been known that electrical signals that are very similar to those that carry information in nerve cells are also observed in plants. It is therefore possible that they reproduce the functions of an animal's nervous system.
Many of the interesting and complicated things our brain does are due to the interconnections between nerves and chemical signals that carry information from one nerve cell to another. The evidence that chemical and electrical signals work together in this way in factories is thin, but could a complex communication network be created in another way?
Some types of electrical signals can flow through the entire facility depending on its transportation system, and the shape of the entire facility and the transportation system that connects it reflects a history of responding to and harmonizing with its environment. The cells of the plant's transport systems have structural interconnections that could carry signals in a complex and flexible way, while the signals themselves appear to be complex, with different triggers that stimulate different and distinctive electrical models.
Thus, electrical signals in plants can have the potential to transport and process information. The problem is that, unfortunately, we know little about whether they actually do it or what their function might be if they did.
An impressive exception is the Venus fly trap. Each trap contains a number of tiny hairs. Every time they are hit, they generate an electrical pulse. Two close impulses close the trap, and three others come closer to crush and digest the prey.
The electrical signals also trigger the dramatic fall of Mimosa pudica leaves and guide the curvature of sticky "tentacles" to trap the prey of insectivorous plants called rossoli. Maybe plants can use nerve signals like animals when they need them, but they usually do things that we find less obvious.
Indeed, by comparing plants with organisms whose mental processes resemble ours, have we made it impossible to recognize a consciousness different from ours? The philosopher Ludwig Wittgenstein said, "If a lion could speak, we wouldn't understand him." To what extent would the "thoughts" of a plant be stranger?
Plants certainly react to their environment in a complex and nuanced way, using information shared between cells of the same plant and their neighbours. They can react to sounds and produce defensive chemicals when they "hear" the caterpillars chewing. Sunflowers follow the sun every day, but they also "remember" where it will rise every morning and turn to welcome it at night. The trees in a forest coordinate with each other, calculating puzzle-shaped patterns in the canopy that optimize the collection of light.
An important question is whether all this could be the result of simple and predetermined answers. Does this "behaviour" require something that might look like our intelligence?
Perhaps true intelligence requires a single command centre to gather data and decide on actions, and an animal-like brain is the only way to create a complex consciousness. Indeed, some definitions of consciousness assume a central identity conscious of itself. Are such things possible without a brain? It has been suggested that the tips of the shoots and roots do this by pumping chemical messages that direct the rest of the plant. But although this can work in a small seedling, a large tree has hundreds or even thousands of shoots and root tips.
Decentralized awareness
What if consciousness could spontaneously emerge from networks of interactions in complex systems? This is speculative, but we have seen that plants can use complex networks of signals to collect and relay information. Without a centralized brain, how strange and incomprehensible such a consciousness could be. Distributed within a federation of cooperating cells rather than under the control of a single general. "We" rather than "I".
Ultimately, all this can be semantic. Authors Lynn Margulis and Dorion Sagan have stated it: "In the simplest sense, consciousness is a consciousness (knowledge) of the outside world. If this is the case, it would be universal for all living beings. What would be different would be the nature of the experience, some simple and others rich and individual. Maybe that's all we can say.
After all, we cannot even "know" what it feels like to be another human being. But the experience of being a plant (or part of a federation of plant cells) would be unimaginably different from ours, and trying to find common terms to describe both may be useless.
