Plants make up 80% of the Earth's biomass, and they've been around much longer than humans. Their survival strategy is completely opposite ours: since we can move, we often deal with problems by avoiding them, favoring quick, short-time solutions. But plants are stuck in place, so they deal with environmental threats and change by adopting much more “deliberate”, long-term solutions.
Perhaps the main difference between animals and plants is that they distribute their core functions over their entire body, while animals concentrate them in specific organs. The decentralized nature of plants makes them "virtually indestructible", whereas animals' organs are points of weakness.
Plants are a living example of how stability and flexibility can be combined. We can learn a lot from them, and perhaps find inspiration to solve many of humanity's problems.
Between four hundred million and one billion years ago, unlike animals, which had to move around to find their food, plants took an evolutionarily opposite direction: they remained in place, getting all the energy necessary to survive from the sun and adapting their bodies to resist predation and outmaneuver the other innumerable constraints arising from being rooted to the ground. That was no easy task. Think how difficult it would be to stay alive in a hostile environment without the ability to move. Imagine you are a plant, surrounded by insects, herbivorous animals, and predators of all kinds, unable to escape from them. The only way to survive would be to become virtually indestructible.
Many of the survival solutions developed by plants are the exact opposite of those developed by the animal world. What is white for animals is black for plants and vice versa. Animals move, plants do not; animals are fast, plants are slow; animals consume, plants produce; animals make CO2, plants use CO2. But the most decisive contrast is also the least known: the difference between concentration and diffusion. Any function that in animals is concentrated in specialized organs is spread throughout the entire body of plants. This is a fundamental structural reason for why plants appear so different from us.
Even though they have nothing akin to a central brain, plants exhibit unmistakable attributes of intelligence. They are able to perceive their surroundings with a greater sensitivity than animals do. They actively compete for the limited resources in the soil and atmosphere; they evaluate their circumstances with precision; they perform sophisticated cost-benefit analyses; and, finally, they define and then take appropriate adaptive actions in response to environmental stimuli. Plants embody a model that is much more durable and innovative than that of animals; they are the living representation of how stability and flexibility can be combined. Their modular, diffused construction is the epitome of modernity: a cooperative, shared structure without any command centers, able to flawlessly resist repeated catastrophic events without losing functionality and adapt very quickly to huge environmental changes.
It isn’t too difficult to imagine that intelligence is not the product of one single organ but that it is inherent to life, whether there is a brain or not. Plants, from this point of view, are the most obvious demonstration of how the vertebrate brain is an “accident,” evolved only in a very small number of living beings—animals—while in the vast majority of life, represented by plant organisms, intelligence—the ability to learn, understand, and react successfully to new or trying situations—has developed without a dedicated organ.
It is impossible to learn without memory, and the ability to learn is one of the requirements of intelligence. Living things are generally capable of learning from experience, and plants are no exception to this principle; they respond in ever more appropriate ways when known problems recur throughout their existence.
Acclimatization, hardening, priming, conditioning, all of them linguistic acrobatics coined over the years by scientists to avoid the use of the comfortable and simple word memory. All plants are capable of learning from experience and therefore have memorization mechanisms.
How such a mechanism works in organisms that have no brain, such as plants, is still a bit of a mystery. Extensive research carried out in the field of stress memory seems to demonstrate the fundamental importance of epigenetics in the formation of this type of memory. Epigenetics refers to certain biological mechanisms that activate some of an organism’s genes while inhibiting the expression of others. In other words, it is the study of changes that alter the way genes behave but not their underlying sequence.
When looking at any plant, we must always remember that we are observing something built on a completely different model from that of an animal—a template so different that, by comparison, all the alien life forms in sci-fi movies are but lighthearted fantasies dreamt up by children. Plants have nothing in common with us; they are different organisms, a life-form whose last common ancestor with animals dates back to six hundred million years ago, a time when, emerging from the water, life conquered land; when plants and animals went their separate ways, taking different paths. While animals developed the ability to move about on land, plants adapted to the new environment by remaining rooted to the ground and using the inexhaustible light produced by the sun as an energy source. Judging from their success, never has there been a happier choice: today there is no environment on our planet that is not colonized by plants, and their share of the total number of living beings is prodigious. There are different estimates—quite variable, as it is not easy to judge the weight of a life—on the amount of plant biomass on Earth, but no estimate is less than 80 percent. That is, at least 80 percent of the weight of all that lives on Earth consists of plants, a statistic that is a measure, unique and unquestionable, of their extraordinary capacity for success.
What are the characteristics of plants that make them so different and incomprehensible? The first, huge difference is that, unlike animals, they do not have single or double organs that are responsible for the main functions of the organism. For plants, rooted to the ground, surviving the attacks of predators is a big problem: because they cannot escape as an animal would, the only way to survive is to resist predation, to not succumb to it. This is easy to say but very difficult to do. To accomplish this miracle, it is necessary to be built differently from an animal. Plants must have no obvious weaknesses, or at least far fewer than animals do. Organs are points of weakness. If a plant had a brain, two lungs, a liver, two kidneys, and so on, it would be destined to succumb to predators—even tiny ones, such as bugs—because an attack on any one of its vital organs would impair the plant’s function. That is why plants do not possess the same organs as animals—not because, as you might think, they are unable to perform the same functions. If plants had eyes, ears, a brain, and lungs, we would not question whether they could see, hear, evaluate, or breathe. Since they do not possess such organs, an effort of imagination is required to understand their sophisticated capabilities. As we have seen, plants distribute over their entire body the functions that animals concentrate in specific organs. Decentralization is the key. We have discovered that plants breathe with their whole body, see with their whole body, feel with their whole body, and evaluate with their whole body. Spreading each function over the entire organism as much as possible is the only way to survive predation, and plants can do it so well that they can even withstand removal of much of their body without losing functionality. Just as a plant does not have organs on which it depends, it does not have a brain that acts as a central control.
The most decisive divergence between animals and plants is that between concentration and diffusion. Certainly, the system of centralization typical of the animal structure guarantees a faster decision-making process. However, although responding promptly may in many cases be an advantage for an animal (though, it must be noted, not for all: well-thought-out responses always require time), speed is an incidental factor in a plant’s life. What is really important for plants is not so much responding quickly but responding well, so as to solve the problem. At first it might seem rash or even unreasonable to argue that plants find better solutions than animals. Yet if you study the question carefully, you will find that animals respond to the most diverse stresses using the same solution every time, a kind of knee-jerk reaction to all emergencies. This reaction has a name: movement. It is a powerful response, like a wonderful card that trumps everything. Whatever the problem, animals resolve it by moving. If there is no nourishment, they go to where it can be found. If the weather gets too hot, too cold, too wet, or too dry, they migrate to where conditions are better suited. If competitors increase in number or become more aggressive, they move to new territories. If there is no partner with which to reproduce, they move in search of one. The list of possibilities is long, even a thousand different emergencies long, to which there is always only one solution: escape. But escape is not a solution; at most it is a way of sidestepping a problem. Animals, therefore, do not solve problems, they simply avoid them more efficiently.
For plants, on the other hand, the question of speed is completely irrelevant. If the environment in which a plant lives becomes cold, hot, or full of predators, the speed inherent in an animal’s response has no meaning for it. What is much more important for the plant is to find an effective solution to the problem, something that will allow it to survive despite the heat, the cold, or the appearance of predators. To succeed in this difficult task, a decentralized, diffused structure is far preferable. As we shall see, this allows for more innovative responses and, being literally rooted, enables a much more refined understanding of the environment. In order to come up with correct responses, it is essential to collect accurate data. It follows that plants, thanks to their choice to be rooted, have developed an exceptional sensitivity. Unable to escape from their environment, they manage to survive only because they can always and with great sophistication perceive a multiplicity of chemical and physical parameters, such as light, gravity, available minerals, moisture, temperature, mechanical stimuli, soil structure, gas composition of the atmosphere, and so on.
There is a mystery still to be solved: How do plants manage without a brain, an organ that underlies every animal response? What systems do they use in its place? And, more generally, how do they manage to produce correct solutions to continuous environmental stimuli? The answer is a rather complex one, starting with the most important organ for rooted organisms: the roots themselves. The root system is, without doubt, the most important part of the plant. It is a physical network whose apexes form a continuously advancing front; a front composed of innumerable tiny command centers, each of which supplements the information gathered during the development of the root and decides the direction of growth.
What is more relevant is that similar structures do not work well. In nature, large, distributed organizations without control centers are always the most efficient. Recent advances in biology on the study of the behavior of groups indicate, beyond a doubt, that decisions made by large numbers of individuals are almost always better than those adopted by a few. In some cases, the ability of groups to solve complex problems is astounding. The idea that democracy is an institution against nature therefore remains just one of the more seductive lies invented by man to justify his (unnatural) thirst for individual power.