Photo: Markus Spiske @unsplash

How conscious are the plants? This is the main question in Daniel Chamovitz's extraordinary new book - What the Plant Knows. Daniel is director of the Plant Bioscience Center at Tel Aviv University. According to him, plants can see, smell and feel, even the plants can be said to have memory. Does this mean that plants can think, or that we can talk about plant neurology? Schamowitz answers these and other exciting questions in an interview with Mind Matters editor Gareth Cook.


How did you become interested in this particular area?


My interest in the similarity between human and plant senses began when I was a young fellow at Yele University's Laboratory. I was beginning to explore how plants sense light to regulate their development. It has been known for decades that flowers use light not only for photosynthesis, but also as a signal that alters their growth pattern. During our research, we found that plants contain a unique group of genes that allow them to understand when they are in the dark and when they are in the light.

Daniel Schamowitz - What the Plant Knows

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Much to our surprise, it later turned out that these genes also exist in human DNA. This inevitably led to the question - what function do these plant-specific genes have in the human body. Years later, we realized that these genes play an important role in humans and animals. They are involved in cell division, neuronal growth and the regular functioning of the immune system.


Most shocking, however, was the discovery that these genes, like plants, regulate our reaction to light in us. Although we do not change our shape in response to light changes, like plants, we are still affected in some way at the level of our internal biological clock, which operates at an 24 clock rate. It is this mechanism of ours that causes us to experience fatigue with a sudden change in time difference, in continental flights, for example. In the absence of these genes in our body, we would not be able to recover from the change in time difference and would be left in a state of fatigue. All these discoveries made me think that, nevertheless, the difference between us and the plants is not that great. This is what made me focus in this area.

Photo: Niilo Isotalo @Unsplash 

How do you think people should change their understanding of plants?


People need to realize that plants are complex organisms that have a life rich in sensations. For many people, plants are no different from stones, for example. We look at them more as inanimate objects, and this is not the case at all. We need to understand that plant biology stems from the constraints that their root system imposes. That is, the plants are "nailed" in one place. They cannot escape in danger or find more favorable conditions - the plants must adapt to survive. This is the reason why they develop an incredibly complex and sensitive mechanism for dealing with the constantly changing environment around them. A mechanism that allows them to "see" their food, "smell" the danger or feel the changes over time. Just because they don't move doesn't mean their world isn't dynamic, on the contrary…


Are you saying that plants have the ability to smell?


Of course! Let me explain what is meant by "smell"! When humans and animals smell something, we actually sense the volatile chemicals that are dissolved in the air and then react in some way to that smell. The same thing happens in plants. The easiest example would be to watch what happens when we put a healthy fruit near rot. You may have noticed that in such situations, the healthy fruit begins to rot too much faster than if it were next to other healthy fruits.


This is because the decayed fruit releases a certain hormone, ethylene, into the air that is sniffed by the fruit near it, even if they are not in the bag, this also happens in nature. Another example of a plant's sense of smell is the parasitic cucumber yarn, which cannot photosynthesize and therefore needs other plants to feed on. The way a "cuckoo yarn" finds its victim is through its sense of smell. This plant has the ability to 'smell' only subtle amounts of chemicals released into the air by neighboring plants. In addition, the "cuckoo yarn" is also pretentious - it selects the plant to attack according to its aroma. For example, the tomato smells much better about "cuckoo yarn" than wheat, which is why it is a preferred nutrient.


Can they hear?


So far there is no stable evidence of this. From an evolutionary point of view, it is pointless for a plant to be able to hear. Consider what hearing is for us and the animals - primarily for the transmission of information and for warning of an imminent danger. Plants use other ways to communicate with each other. Even if they could hear the approaching danger, they could not escape or hide. However, recent studies in this regard indicate that plants may respond to sound. Not as much music as is popularly claimed at the moment, but rather certain vibrations. It will be interesting for me to follow the development of these studies, which, as I said, are still very much in the beginning.


How do plants communicate with each other?


Through the signals they send! For example, maple trees, when attacked by bugs, release a certain pheromone that is perceived by other trees. Due to this, they begin to release special protective chemicals that repel the attackers. It is not clear, however, whether the first tree attacked begins to release these pheromones to protect the remaining trees or to protect its own branches that have not yet been attacked.


Another example of plant communication is the result of a recent study where plants transmit signals to one another through their root system. In this case, the "informant" was subjected to a stressful situation left on land for a long time. The plant warns neighboring plants to "prepare" for a small amount of water. We know that the signal went through the root system because the effect did not occur with plants in pots adjacent to each other.


Do plants have memory?


Plants definitely have several different types of memory, just like humans. They have short-term memory, immune memory and even memory passed down through generations. For some people, this can be a difficult concept to digest. If you look at memory as the processes of encoding, storing and reproducing information, then we can certainly say that plants can remember! For example, the flycatcher closes when at least two of its tentacles are touched by a fly. The Flycatcher remembers when one of her tentacles was touched and keeps that memory for about 20 seconds. If you tap another one during this time, it will close. Some plants, however, that have been exposed to stressful situations give birth to generations more resilient to these same situations.


Would you say that plants can "think"?


No! But of course this is my personal opinion. For me, thinking and processing information are two different processes. I think conscious thinking is a process that requires advanced brain function. This, in my opinion, does not exist in plants, at least because they have no brain. For the same reason, they do not feel pain after the sensation of pain is formed in the brain.


Do you see any analogy between what plants do and what the human brain does? Can we talk about plant neurology, but without neurons?


I'm not sure that a term like "plant neurology" is appropriate. Plants do not have neurons, however they find other ways of transmitting information about the cellular, physical, or even environmental state. For example, root growth depends on a hormonal signal produced at the tip of the shoots and is then transported to the roots. The leaves, however, send signals to buds when to start to bloom.


In this way, an analogy with the human brain can be drawn, it can be said that the whole plant behaves like a brain. Although they do not have neurons, they produce and are affected by neuroactive chemicals. For example, the glutamate receptor is a neuroreceptor in the human brain that is required for memory formation and for learning new things. As I said, plants do not have neurons. But they have glutamate receptors, and what's more interesting - the same substances that suppress glutamate receptors in humans also affect plants.


Even Darwin had hypothesized that the ends of the roots in plants act as a "root brain". They act as the brain in the lower animals, that is, they can accept sensations and direct movements. Many modern research groups are still engaged in this research. It will be interesting to find out what the findings will lead to!



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