The question do plants feel pain is an important one for those who care about all life on our planet and want to be as ethical and possible in how they eat.
Unfortunately, the short answer is that we just don’t know – at least not yet. Really, however, the question is far more complicated than you may imagine.
And the more we learn from scientists about plants and their behaviors and interactions, the more we realize how complex and amazing the plant world can be – and how little we really understand that world, whose mechanisms are often so different to our own.
One of the main problems with saying whether plants feel pain is in determining how ‘pain’ should be defined. Pain is usually defined as a highly unpleasant physical sensation. This definition focuses on how that feels to us, rather than on any physical or physiological response.
This makes it difficult to determine whether pain means the same to plants – can they feel? The truth is, we just don’t know.
DO PLANTS HAVE NERVES?
The problem with defining ‘pain’ is that plants are composed very differently to us. However, the way they ‘sense’ and ‘respond’ to stimuli is actually surprisingly similar. Plants do not have a nervous system and brain like an animal.
Researchers have discovered that specialized cells called bundle-sheath cells can communicate electrical impulses.
These operate in much the same way as nerve cells in a human or other animal. This electrical signalling is the focus of much current scientific research. The electrical impulses are called action potentials and are just the same as the electrical impulses in our own nervous systems.
All biological cells, be they animal or plant, are electrical.
The electrical signalling may be like a nervous system in some ways, but it is not easy to link those signals to specific functions in the plant and the biology community is not even close to reaching a consensus about how those impulses are used.
So, when discussing whether plants feel pain, all we can say with certainty is that they do not feel in quite the same way we do.
We understand little at present about how plants ‘feel’ any stimulus.
We can, however, say with some certainty that they do react to stimuli.
Plant movements are better understood and tell us a lot about how plants are able to respond to the world around them.
Here is a description of various types of plant movement, to help you better understand how plants react to sensory stimulation. (Whether or not they ‘feel’ it in a way that would be meaningful to us.)
Phototropism is the word given to the simple idea that plants shoots will always grow towards light.
When light hits photoreceptors on the plants, this translates biochemically into a growth response, which will make plants react to the stimulus and bend towards light.
Geotropism, or Gravitropism, is the word used to describe the turning or growth movement of a plant in response to gravity.
Roots will always grow in the direction of gravity, even when you turn a plant on its side. Plants react to gravity, by releasing hormones that change the rate of cellular growth in their tissues.
Thigmotropism is the word used to describe the turning or bending, or directional growth movement of a plant which occurs as a mechanosensory response to touch stimuli.
This is the mechanism by which climbing vines and plants such as peas hook onto supports, curling their tendrils around the first thing they touch.
Roots also rely on touch to work their way through the soil – when they touch an object they will grow away from it, allowing them to find a path of least resistance through the ground.
Hydrotropism is the response of plants to water. Again, growth response is initiated – for example, in the growth or turning of plant roots towards or away from water. The root cap senses water and sends a signal to the growing part of the root.
This mechanism is difficult to observe in underground roots, where gravitrophism is generally the stronger impetus, though it has been shown in labs and could be important for plants grown in space, in a microgravity environment.
This is the response of a plant to a chemical stimuli, either from within the organism or from outside it. The conversion of flower into fruit is an example of this sort of plant reaction. This is another change in response to sensory information that the plant is receiving.
Plants will also respond to a change in temperature.
Thermotropism is the movement growth response to heat or cold.
One common example is the curling of rhododendron leaves in response to cold temperatures.
The precise biological mechanism for this movement is not yet fully understood, but it may be related to the transfer of ions through cell membranes and the electrical action of cells.
This is the response we see in sunflowers, and other plants, which can turn their ‘heads’ to face the sun in order to maximize the amount of light hitting photoreceptors each day.
Recent research conducted into suggests that plants can ‘hear’ and respond when caterpillars are eating them. Previous studies have suggested that plants react to sound vibrations on their leaves, and this study has shown the chemical plant response, the ‘defence mechanism‘, to the specific sounds the caterpillar makes while munching on the leaves.
DO PLANTS FEEL PAIN?
Plants perceive the world without a brain, eyes, ears or a nervous system but the more we learn about plant reactions and responses to stimuli, the more we realize that plants are far more complex than most people believe. They can ‘see’, ‘hear’ and react to the world around them.
We do not really know whether they experience pain or physical sensations in any way that would be meaningful to us, but we do know that they react to a whole range of sensory experiences, as well as exhibiting a whole range of other ‘animal-like’ behaviors.
They seek out food, protect themselves against attack, evade danger, communicate with their neighbors and fight for territory – they just do it all far slower than animals do.
Plants move with purpose, so they are in some sense ‘aware’ of the world around them. They are extremely sophisticated organisms about which we know relatively little, even today.
We cannot know whether plants feel pain, or whether they have any ‘identity’ of their own as individuals unless we develop ways of communicating with them. Who knows whether that would ever be possible – but if it were – just imagine the tales they could tell!
The gulf between the plant and animal worlds is immense – but more things connect the two worlds than many of us like to think.
We have a lot on common with plants – far more than we may like to admit.
They are living beings just as we are, all part of the great whole.
Of course we need to consume plants for sustenance – that is part of our biological make up.
But we should respect their biology, their beauty, their complexity and think of them as more than just our dinner, or as the background of our daily lives.
In case they do feel pain, we should always be humane.
PULLING IT ALL TOGETHER
Choosing fruits, nuts or berries that fall from trees and other plants as a proportion of our diets will help to avoid unnecessary destruction, whether there is suffering or not. But we cannot survive on just those nutrients and remain healthy.
Whether or not you choose to eat plants, whether or not they truly feel pain, we should give plants the respect they deserve and share our space with them in a harmonious and thoughtful way, just as we should with all animal life on this planet.