You may have heard at some point in your life that “plants have feelings too.” Although this can be deemed valid to a certain extent, it’s highly debatable. Plants have a completely different genetic makeup than humans, so is it really true that plants can feel pain like we do?
Plants can’t feel pain. Plants don’t have a brain or a central nervous system, which we humans use to process pain. Given that plants don’t have neurons or a central/peripheral nervous system, they don’t have pain receptors and ultimately don’t process/feel pain.
In this article, I’ll dive further into the points made above and discuss the genetic makeup of plants and why they’re unable to feel pain. Keep reading to find out how plants differ from humans in terms of registering pain!
Why Plants Can’t Feel Pain
Since plants are living creatures, it can be easy to assume that they are sentient, similar to humans and animals.
Although plants undergo the seven life processes (movement, respiration, sensitivity to stimuli, nutrition, excretion, reproduction, and growth) and are classified as living organisms, there are a few specific elements that differentiate them from humans and animals.
Functions of the Nervous System
Before I get into how a plant not having a nervous system affects them in terms of pain, I’ll first explain the functions of a nervous system. Learning the purpose of a nervous system will help you understand why plants can’t feel pain.
The human nervous system is split into two parts: the peripheral and central nervous system. These two nervous systems are split up further, but I’ll only discuss the parts responsible for processing sensation.
The Central Nervous System
The central nervous system (CNS) consists of the brain and spinal cord. The CNS is responsible for interpreting information from the external environment and controlling voluntary and involuntary movements such as walking (voluntary) and breathing (involuntary).
The spinal cord serves as a channel for signals between the brain and the body. Damage to the CNS can result in the inability to interpret signals and sensations and, thus, the inability to respond accordingly.
The Peripheral Nervous System
The peripheral nervous system (PNS) consists of nerves that form the communication between the CNS and the rest of your body. The PNS comprises sensory nerves that allow us to feel sensations and pain.
The PNS has nerve cells/neurons that act as information processing units that receive and carry messages to other neurons. Since the PNS consists of sensory nerves that allow us to feel pain and other sensations, damage to the PNS can result in issues such as numbness and muscle weakness.
The points above are merely brief descriptions of the functions of the nervous system. Now that you have a general overview of the purpose of a nervous system, I’ll explain how this relates to a plant’s inability to feel pain.
Plants Don’t Have a Central or Peripheral Nervous System
A plant’s inability to interpret and process pain stems from its absence of a nervous system. As we now know, the brain, spinal cord, and sensory nerves are responsible for pain signals and how one responds to them.
A plant’s lack of nerve cells/sensory nerves makes them incapable of processing and feeling pain like humans and animals do. It can be argued that plants have something similar to a nervous system, but I’ll get into that later.
Plants Don’t Have Nociceptors
A nociceptor is a sensory receptor that registers painful stimuli. Nociceptors are specialized peripheral sensory neurons responsible for processing and responding to harmful/painful stimuli, yet another reason why plants can’t feel pain.
Plants lack the machinery and receptors responsible for being aware that something is painful. Although plants are living creatures, they don’t have the same level of consciousness as humans and animals do. If plants were as conscious as animals and humans, you’d probably feel terrible for going strawberry picking or being a farmer.
A Plant Doesn’t Have a Brain
A plant not having a brain is probably one of the most significant contributing factors to why they can’t feel pain. The brain is in control of practically everything. Anything you do and think of doing is processed in the brain first.
Since plants don’t have a brain, they can’t be made aware that something hurts. Brain mechanics is why people with brain damage often lose feeling in certain parts of their bodies.
Someone could try to hurt them severely in the numb body part, and they wouldn’t feel anything. Why? Because damage to certain parts of the brain or spinal cord prevents pain signals from being transmitted.
Given that plants don’t have brains and don’t receive pain signals, you can think of them as constantly numb to painful stimuli. However, a plant has a command center in the root, which can be described as its “brain.”
How Plants Respond to Stimuli
This is where things get a little more technical. Although plants don’t have a typical nervous system and, thus, don’t have sensory nerves that detect pain, they still respond to stimuli using their own kind of “nervous system.”
Plants Generate Electrical Impulses in Response to Stimuli
Plants generate electrical impulses otherwise known as action potentials. According to the National Library of Medicine, an action potential is a rapid sequence of changes in the voltage across a membrane. An action potential can occur in several types of animal and plant cells.
To help you better understand what an action potential is in plants, I’ll give you an example of it in humans. For example, an action potential occurs when we touch something sharp or hot. Our sensory cells that are responsible for touch trigger action potentials, which send a signal to our brain that we’re feeling something hot/sharp and allow us to remove our hands immediately.
Although plants don’t have nerves, you can think of their electrical impulses as such. A plant’s lack of a brain and nervous system doesn’t mean it cannot respond to external stimuli. If plants were non-responsive to stimuli, they’d all be dead (so would we), as photosynthesis wouldn’t occur.
For example, when an aphid (a tiny, sap-feeding insect) attacks a leaf, this phenomenon triggers an electrical signal that travels from leaf to leaf that tells the plant to start protecting/defending itself. Pretty intelligent for an organism that doesn’t have a typical brain!
How Plants Protect Themselves Against “Pain”
First things first, a plant doesn’t determine that something is “painful.” Although sap-sucking insects attacking a leaf could be considered painful to humans, a plant sees it as more of a threat than anything else. Since plants don’t have nociceptors, they can’t process the aphid attack into a painful experience.
So, how do plants protect themselves? Still using the aphid attack as an example, plants resistant to aphids display an increase in callose deposit. Callose is a compound found in the cell walls of various plants that inhibit the food source for aphids.
Aphids end up ingesting the callose deposits through the sap they feed on, which results in their death. It’s important to note that although plants have a certain level of awareness and can decide whether something is a threat, they can’t process these threats and attacks as something painful. Their inability to interpret and process pain can be seen as a massive advantage in the plant and animal world.
Examples of a Potential Nervous System in Plants
I mentioned earlier that it could be argued that plants have something similar to a nervous system. Although the definition of consciousness and a nervous system has boiled down to only being seen in animals and humans, some researchers allude that plants have a “simple nervous system.”
Such claims are up for debate and can be controversial. However, the definition of a nervous system can be broadened regarding plants. That said, I’m going to discuss two plants in particular that exhibit a remarkable level of consciousness and could end up interpreting pain with enough evolution.
The Venus Flytrap
The Venus Flytrap (Dionaea muscipula) has been studied in-depth, and some amazing conclusions have been made. The Venus Flytrap uses its leaves to capture insects, but first, it must make particular distinctions.
Venus Flytrap Differentiates Its Prey From Other Objects
Before the flytrap closes on its prey, it must first decide whether the object is actually prey to prevent it from closing on inanimate objects. The distinction a Venus Flytrap makes between foodstuff and useless things like sand or debris is already a portrayal of immense intelligence.
The Venus Flytrap has to make predictions to succeed in its predatory ways, ultimately exhibiting a calculated thought process.
A Venus Flytrap Uses Mechanical Stimuli To Make Distinctions
A mechanical stimulus is a stimulus produced by physical changes. The changes can include:
- Changes in pressure
- Contact with other objects
What we can conclude from a flytrap responding to mechanical stimuli is that they have mechanoreceptors, a sensory receptor that responds to mechanical pressure. A Venus Flytrap registers two mechanical stimuli to distinguish between prey and other objects within less than a minute.
The flytrap’s leaves first enter a semi-closed state once pressure/movement is detected. The plant then has to decide whether the object in its leaves is worth fully closing for. The plant won’t register additional signals (think of the electrical impulses/action potential) if the insect is small enough to escape through the gaps of the plant.
If the plant decides the insect is of the appropriate size, it’ll register additional mechanical stimuli, and the leaves will close entirely. The Venus Flytrap can switch from semi-closed to fully closed within split seconds.
A Venus Flytrap Responds to Electrical Signals
A Venus Flytrap also receives and processes electrical signals and acts based on them. The difference between a flytrap and some other plants is that a flytrap has sensory receptors that can determine when it’s being touched or moved.
Mechanoreceptors could be seen as a part of some kind of nervous system in plants, ultimately raising the possibility of plants having their own nervous system. A Venus Flytrap uses its cells’ electrical state to process information, allowing for a range of predatory reactions.
Although a Venus Flytrap is unique, it’s not an anomaly. Despite exhibiting a range of interesting features, other carnivorous plants, such as the Bladderworts (Utricularia), also use electrical impulses to perform predatory actions.
The Shameplant (Mimosa pudica), also referred to as the sensitive plant or touch-me-not, is an anti predatory plant. Like the Venus Flytrap, the Shameplant also has mechanoreceptors that detect when it’s being touched or moved. However, the Shameplant doesn’t fight back.
Mimosa Pudica Exhibits Antipredatory Behavior
In contrast to the Venus Flytrap, a Shameplant has no desire to feed on potential predators.
The Shameplant registers electrical signals to exhibit antipredatory behavior that protects them rather than capturing the predator and killing them.
The Shameplant Folds Inward When Touched
Using the same mechanoreceptors as a Venus Flytrap, the sensitive plant sees stimulation as a potential threat and uses electrical signaling that tells the plant’s leaves to close. The Shameplant can also be triggered to fold inward when humans touch it and slowly opens up again a little while after being triggered to protect itself.
Since the plant’s leaves fold inward when stimulated, the surface area of the leaves is reduced, giving the potential predator not much room to attack. Suppose the potential predator stays on the plant even after the leaves close and stimulation continues. In that case, the Shameplant will start dropping its petiole (the stalk that attaches the leaf to the stem of the plant) in an attempt to cause the potential threat to fall off the plant’s leaves.
Once the potential predator has fallen off the plant, the leaves will remain closed for however long after and open back up once electrical signals say it’s okay to do so. The time they stay closed is known as their hiding time. A mind blowing fact is that the mimosa pudica’s anti predatory behavior is condition-dependent, just like with animals.
To a certain extent, condition dependence could be described as a variation, as each individual Shameplant can exhibit a different hiding time.
How a Potential Nervous System in Plants Relates to Pain
You may be wondering how the examples mentioned above of carnivorous and non-carnivorous plants are relevant to a plant’s ability to feel pain. Well, mechanoreceptors are a type of somatosensory receptors. Somatosensory relates to the conscious perception of temperature, motion, pressure, and sound waves. Basically, the ability to interpret sensation.
The fact that certain plants are mechanoreceptive can be seen as indicative of a potential nervous system. The possibility of a potential nervous system in plants is significant in evolutionary biology, as nervous systems are only ever recognized in humans and animals.
The presence of a nervous system in plants would mean that they’ll be able to interpret and process pain, which has never been seen before. Although plants can send out distress signals (like when the grass is cut), there’s no way of telling whether the said plant is in pain.
As aforementioned, plants don’t have the sensory receptors responsible for processing pain (nociceptors). So, even if a plant sends out distress signals when it’s being chopped down, there’s a low chance of the plant being in pain. It’s simply aware that something dangerous is happening and may act to protect/defend itself against the threat.
Responses to Stimuli Could Be Related to a Nervous System
Stimulus-response coordination is related to the nervous system. A human’s fight, flight, or freeze response comes from the nervous system. Given that plants harbor various reactions to various stimuli, it can be deemed accurate that plants have a “simple nervous system.”
A nervous system can be described as the body’s command center, and since plants have a command center in the root, it isn’t far-fetched to say that plants have a simple nervous system. However, a plant’s nervous system likely wouldn’t be as advanced as its human or animal equivalent.
For a plant to be so advanced that it can interpret and process pain like animals and humans, it would probably take over a lifetime of evolution. While plants have intricate genetic makeups and undergo various processes that prove their evolution and intelligence, they are physically unable to feel pain. Although plants can respond to a range of stimuli, they don’t have the nerve cells that allow for the interpretation of painful stimuli.
Plants are highly intelligent organisms, and their evolution over the years is certainly notable. Although there have been many debates between researchers and botanists regarding the genetic makeup of plants and how they interpret and process information, the existence of a brain and nervous system within a plant can be subjective.
Some may believe that a plant has a nervous system and can thus feel pain because it can respond to stimuli. However, the fact of the matter is that plants cannot feel pain. I hope this article has helped you understand why plants can’t feel pain!