A rose, a fern, a mushroom, a moss, aspen, a big oak tree, what are they thinking? This question sounds strange at first, and even overwhelming. Can you imagine yourself as a plant? Although he is still alive, he has legs that can walk, no arms that can stretch, no eyes to see the scenery, no nose to smell, no mouth to eat… The most important thing is that there is no brain!
Plants are nailed to the ground, and life is restricted everywhere and cannot be moved. It looks stupid. Besides growing and declining with the sun and the moon, what else can they do? What thoughts can they have? But appearance can deceive! In the recent period, some new types of botanists have not only discovered that plants display intelligence, but also revealed their cognitive roots, thus laying the foundation for a rapidly developing new scientific field, that is, plant cognition.
Italian researcher Stefano Mancuso is the co-author of a groundbreaking paper in this field in 2006. He said with satisfaction: «In recent years, many papers have been published on plant intelligence and the ability of plants to process large amounts of information related to the environment. And more and more More young biologists, physicists, and informatics have shown interest in this.»
The 2006 paper evoked a strong response as soon as it was published. Is «Autonomic Neurobiology» established? Can grass be given intelligence? At that time, 36 scientists published articles in academic journals to object to this analogy. In their view, this practice of applying a concept exclusive to the animal kingdom to the plant kingdom is simply incomprehensible. «We urge the fans of autonomic neurobiology to regain their critical spirit and base this concept on a rigorous knowledge base,» they exclaimed.
Darwin’s definition
When there is a misunderstanding, it is usually necessary to agree on the words first. Start with the concept of intelligence. «I personally changed my view on this issue.» Francis Hallé admitted. He has always actively defended the dignity of our green relatives, and he once had reservations about the use of the word «smart» when talking about plants: «I was loyal to my education at the time and abide by the definition of the word «smart» in the dictionary. But as far as this definition is concerned, humans are both judges and parties. So now I accept a broader definition of intelligence, not to mention Darwin also used it.» In the eyes of the founders of the theory of evolution, the main characteristic of possessing intelligence is Being able to act smartly, there is no limit as to how it can be used. «Let’s not forget that intelligence problems will only arise when we observe the so-called intelligent behaviour of organisms.» pointed out Paco Calvo, head of the Minimal Intelligence Laboratory at the University of Murcia in Spain, philosopher and botanist.
British botanist Anthony Trewavas defended the pioneering work of his Italian counterparts with his academic reputation and put cognitive biology on the track of Darwin’s point of view: “I think plant intelligence is firstly related to their ability to survive in the environment, and It means the ability to solve special problems related to its survival.» He said bluntly: «Even neuroscientists describe some behaviours of plants as basic forms of intelligence.»
Keeping up with the slow pace of plant growth, botanists have obtained unquestionable observations: all branches looking for light are like snakes swimming towards their prey; even the smallest shrubs have memories, they can make decisions communicate with their neighbours, and when needed Can help each other.
Plants take root in one place throughout their lives and develop a set of amazing intelligent behaviours in long-term evolution to counter the impermanence and dangers of nature. “Natural selection works first on individuals, like pulling weeds to remove individuals in each generation who cannot show the lowest level of survival intelligence.” Anthony Travis explained in detail, “Each plant continuously perceives the environment and processes each This kind of information, use your memory to make the best decisions, and improve your survival rate.» A brief ancient motto guides this intelligence: growth and resistance. But is that all? Thought cannot be reduced to just a maxim. To understand the thoughts of plants more deeply, one should not just observe their external behaviours but should study the internal mechanisms that underlie the behaviours. In other words, replace the overly general «intelligence» with the more experimental «cognition».
According to the definition put forward by the American zoologist Sara Shettleworth, “cognition is related to the mechanism by which animals acquire, process, and store environmental-related information, and act according to this information, involving the functions of perception, learning, memory, and decision-making.”
In the animal kingdom (except for sponges and silkworms), cognitive functions are realized by neurons and glial cells. These special cells exchange information through chemical or electronic channels and rely on complex interactive networks to process information.
Currently, scientists are capturing these functions of plants. This hunt is almost a feat. Because to study the way of thinking of animals, you only need to pay attention to the operation of their brains, but were to observe the cognitive mechanism of plants? «Plants do not have centralized organs like our brains, nor do they have neurons, but it does not mean that they do not have certain equivalent functions.» Stefano Mancuso said, «For example, they have no lungs, but The same can breathe. These functions are scattered throughout the plant, scattered in their cells, and we must look for it in this direction.»
«To show the lowest level of intelligence, you must be able to receive and process information, and make the processing results persist in the cells.» University of California neuroscientist and mollusc basic cognitive mechanism expert David Glanzman pointed out.
It is not easy for our minds to face such a completely different way of thinking. Imagine that your perception of the environment and information processing originates from the interaction of a large number of cells scattered throughout the body…
Three functions have been identified
Efforts to live in harmony with the plant world are expected to encounter setbacks here. «Neuroscience has been unable to absorb Darwin’s principle, that the same biological function can take different forms.» Australian cognitive biology pioneer Pamela Lyon revealed.
The resistance is disappearing. Of course, among die-hard «neurobiologists» and prudent botanists, the status of plant cognition is still controversial. But the words are not important! With the help of technological advances in cell biology, molecular biology, gene sequencing, imaging, and bioinformatics, plant experts are discovering cellular information-processing mechanisms that have never been thought of before.
From this we begin to understand how the three basic functions of plant cognition are organized: memory enables plants to record all types of information; learning to make the best use of this information; decision-making to make them make the best choices.
How does the seed determine germination? How does the branch remember the temperature? How does the plant learn to distinguish nutrients? Some recent discoveries outline the answer, surprising and fascinating, and finally, enable us to describe how a tree becomes a tree—of course to the current level of knowledge.
Let us dive into these three typical plant thinking.
Plants make choices, make real decisions
«We couldn’t believe it at first. This is a fantasy story.» George Bassel of the University of Birmingham said with satisfaction. The British researcher, who defines himself as a «computational biologist,» by studying the root cause of all the decisions made in the plant’s life, sprouting, and his team achieved a pioneering initiative: observe from the molecular level how plants weigh the pros and cons before heading for the light. «This research is wonderful! It is the first time to show the decision-making mechanism of plants in detail.» Stefano Mancuso, a pioneer in the field of plant cognition and an Italian scholar, praised.
Hormone battle
Decision-making is a grand research topic of neuroscience, a basic process that everyone goes through thousands of times every day. Balzac wrote: «Choice is the lightning of wisdom.» Wisdom—intelligence, the word itself consists of Latin inter and Legere, which literally means «choose among them.» Plants also make many decisions, because they have to! Plants continue to interact with the environment, but they cannot carry away people when danger comes. Therefore, in order to survive, it is necessary to maximize the use of the environment at every moment and every season.
«Even if the wrong choice does not have immediate negative consequences, its energy cost will ultimately affect the performance of the plant.» British botanist Anthony Truvas emphasized. This mechanism operates according to the plant time which is far from ours, leading to «people have long underestimated the plant’s ability to understand external information and make the most beneficial decisions for the future.»
And there is another question: Which part of the plant should be studied to observe this mechanism? George Basel elegantly circumvents this problem by studying the decision of a seed. Because all the cells of the plant are concentrated in the same entity at this time, and because the seed only needs to make one major decision: to germinate or not to germinate.
We already know that the seed, like its mother plant, can perceive changes in the environment over time (temperature, humidity, nutrition, etc.) quite keenly. But this is not all. Because the seed must avoid hasty decisions. For example, there are a few days of abnormal warming in the cold winter, making it think that spring is coming, it may become unsatisfactory and start to sprout! And the coming cold current will freeze its spring-like enthusiasm. At this time it can only «see the roots and sigh»-to be more precise, it is just a radicle!
Don’t worry, but decide what to do or not to do-plants have this ability. George Basel observed this in the seeds of Arabidopsis thaliana, the star of the plant laboratory. This kind of child is not a novice: before the probe goes out, it carefully handles external information, turning the roots around several times. «There is a veritable decision-making centre at the top of the radicle, constantly weighing advantages and disadvantages. It has the same spatial organization as some very simple cognitive systems in the human brain.» The researcher said.
To reiterate, there are no neurons and no synapses here. Thinking is more like a hormonal battle between cells that favour «sprouting» and cells that favour «non-sprouting». «Non-germinating» cells are located on the surface of the radicle and are more sensitive to cold. The colder, the more abscisic acid, or «sleep hormone,» produced by these cells. In contrast, the cells located in the warm centre of the radicle require resuscitation to produce the growth hormone gibberellin. There would be no results in this battle,
If it weren’t for a carrier protein to spread these two hormones to each other’s territory indiscriminately, causing chaos.
Just like computer computing
«The arrival of one hormone will inhibit the production of another hormone, forming a complex dynamic system.» George Basel continued, «We confirmed that only such a spatial organization can prevent plants from reacting hastily. In the end, only in It is only after major fluctuations in temperature that you decide to germinate.» The seed is not stupid, it will brew its own choice in a series of warm weather harbingers.
«In addition, the same mechanism may control other decisions related to plant growth.» George Basel thinks so. Such decision-making centres may be scattered throughout the plant to better guide growth according to different signals from the outside world: light, temperature, whether there are mineral resources, etc.
«Plant cells and grid computing are magically similar: each cell is responsible for its own part of the information processing work so that the system as a whole can make the best decision.» George Basel from the field of information science hopes to rely on this analogy, And finally reveal other information processing mechanisms of plants. Before that, we can think that when a plant does something, it is because it made a decision.
They have memories
«In my opinion,’ plant memory‘ is not more surprising than the term computer memory’.» Michel Thellier, an emeritus professor at the University of Rouen in France and one of the pioneers in the field of plant cognition, points out, «plant memory is by no means a weird one. Conceptually, it seems to play a key role in the adaptation of plants to the environment.»
However, the popularization of this concept is not easy. In the early 1980s, when Michel Trier submitted his early research on this issue for peer review, some scientific journals closed the door to him: «I regretted using the word memory for a while. But then it proved that I was right. .»
This is because, in the face of environmental threats or repeated offenders, plants have every reason to have memories. What about the evidence? Remember that water starts to become scarce to better protect corn against drought; remember that being attacked by a pathogen allows tomatoes to defend themselves more quickly when encountering a new attack; finally, remember that wind and the risk of being uprooted Poplar trees are more firmly rooted in the soil and more cautious when growing branches. And these are just a few examples that have been proven.
This kind of memory is not the same type as ours. «The difference with humans is that the memory stored by plants is closer to a preset recovery, that is, a certain instruction, rather than recreating the past like our memory.» Michel Trier explained. Nevertheless, this memory mechanism in plants also uses a strategy seen in human neurons: epigenetic reprogramming.
This reprogramming first acts on the spatial and chemical characterization of plant cell nuclear DNA. «At present, we know that epigenetic reprogramming in animals not only assists memory but also strengthens synaptic connections. The discovery in plants shows that it is universal.» Neuroscientist David Glanzman of the University of California, Los Angeles, USA Introduced.
The Secret of «Vernalization»
In 2015, scientists discovered this mechanism in Arabidopsis for the first time. «A beautiful surprise»-Caroline Dean, a cell biologist at the John Innes Center in Norwich, England, recalled that she discovered that this plant has memories of cold. Like many agricultural crops such as wheat, Arabidopsis thaliana blooms in spring only when it has a memory of overwintering. Scientists call it «vernalization».
To put it bluntly: Plants’ memories of the arrival and duration of cold can last for several months. When the temperature starts to drop below 5°C, there is one gene that will become a target in all cells, and that is the FLC gene. It encodes a hormone that controls the flowering of this plant and is especially active in spring. The memory of the arrival of winter will appear as a chemical change in the chromatin surrounding the gene, and this change will exist for a long time until spring.
«It is worth noting that this pair of cold binary memories will be activated independently and persistently in each cell of the plant, forming an overall memory reflecting the length and intensity of winter.» Caroline Dean explained. At the cellular level, winter memory is binary, like a simple switch, while at the plant level, winter memory is extremely precise. This strategy is similar to computer memory. It uses a long string of 0s and 1s to store a decimal number with multiple decimal places. «This precision especially allows plants to distinguish whether it is a cold wave in autumn or a real winter.» Caroline Dean clearly pointed out.
The arrival of spring reactivates the FLC gene in each cell and gradually «forgets» the past winter, but this seasonal reverse forgetting process of memory is still unknown to researchers. «At present, plant memory researchers are still mainly at the descriptive stage, and we are far from understanding the subtleties of related mechanisms.» Admitted Mark Zander, a cell biologist at the Salk Institute in the United States who studies the epigenetic changes in Arabidopsis. «But this is definitely the most effective mechanism for plants to remember information.»
Michel Trier even vaguely anticipated some of its application directions: «A better understanding of these processes can eventually open up new directions in agronomy.»
Learn from experience
The flowers of passionflower are really beautiful. But what attracted Francis Alley was not only the spring appearance of this climbing vine but also its amazing ability to learn from its mistakes: «This is an excellent example of intelligent behaviour.»
The French botanist invited us to play with the passionflower and plant a bamboo a few centimetres away from a new bud: «It first stretches out a tendril, which is similar to a lasso, to get close to the support and climb. If you move the bamboo slightly to the right, the vines will follow. Now please note: If you repeat this operation five to six times, the vines will actively predict the advance and stretch directly to the right side of the bamboo. After that, Passionflower learned to stop being deceived.
«This example is an excellent demonstration of the predictive ability of plants, and we have already observed this phenomenon in root development.» British botanist Anthony Truvas said happily. He also developed a strong interest in this small vine plant. Some neurologists also sent him an email consultation. How can a plant show such learning ability?
Experts in plant cognition do not yet have a clear idea. «Learning requires both memory and decision-making, so it is very likely to produce the same molecular process.» Monica Gagliano, a plant behaviour expert at the University of Western Australia, said.
The young researcher was originally an animal behaviour expert. This background must have inspired her to carry out the most amazing plant learning experiment, which we can call «Pavlov’s pea».
In the famous experiment conducted by Russian biologist Pavlov in the early 20th century, the subject was a dog. Ringing the bell first, and then giving food to the dog. After several repetitions, he found that even just ringing the bell and no food was enough to make the dog salivate. Dogs have learned to associate ringtones with rewards. Now scientists have discovered that Pea seems to be able to achieve this «associative learning» too!
Change paradigm
Monica Gagliano measured the ability of pea seedlings to predict light based on a seemingly neutral sign-wind. In her experiment, whenever the wind blows to one side of the plant, the light will shine on the same side. As a result, just like dogs, Germ learned to associate wind and light in most cases.
From the statistical data, the effect of this learning is not as good as that of dogs: slightly more than 60% of pea shoots have learned experience, while more than 90% of dogs. «It should be more comparable.» Monica Gagoriano defended. «When plants choose to follow the wind, they are more against their own nature than dogs. They made a risky decision, in terms of energy. It may cost a lot.»
«The research has caused controversy, but it must be admitted that these conclusions can withstand critical analysis.» Bruno Moulia, a researcher at the French National Institute of Agriculture (INRA) commented. He decided to repeat this experiment in his own laboratory: «If it can be verified, it can open up another world for us and bring a veritable paradigm change.»
In fact, we already know that plants can perform so-called «primary» learning. Some are through habit, mimosa is an example. Mimosa is also called induction grass, which means that its leaves will close together with a light touch. Mimosa can learn to no longer be afraid of repeated shaking eventually harmless. Some are sensitized. For example, many plants can learn to defend themselves more quickly when a pathogen strikes for the second time.
More chances of survival
Pavlovian learning makes Pea connect two independent stimuli, which is a higher cognitive ability. In fact, neuroscientists generally speculate that associative learning, which has so far been regarded as animal characteristics, is one of the key links connecting more complex behaviours. For example, the orangutan’s hobby for nuts can be guided by a series of associations to the use of tools-using stones as walnut clamps. But in the world of plants, what can they get from such cognitive abilities?
«In a complex and changeable environment, being able to use supplementary information to better locate resources, especially light, will greatly increase the chances of survival.» Monica Gagliano explained. Just as predators learn to better use different predictive information to track their prey, plants that face the same natural selection as animals may also develop the same learning ability.