Plants and sensetivity to pain.

Apparently there has been evidence (not particularly new by any stretch of the imagination but I've only recently stumbled upon it) to show that plants respond to stimuli- with some sources going so far as to claim that they feel pain.

So before I delve into this research, I should point out that I don't understand how this logically is a possibility. To feel pain, you need to be conscious. Maybe you don't need to be sentient or sapient but consciousness is a prerequisite. Since plants have no brains, hence no cerebral cortexes, they can't be conscious. This begs the question: if they aren't conscious, how do they feel pain?

Even is they do feel respond to stimuli (which they probably do), I don't see how we could empirically conclude that they feel "pain" in a way that is equivocal to the way we do. Humans and plants have completely different neurobiolgy and anatomy. Humans feel empathy because of mirror neurons* (which are neurons that fires both when an animal acts and when the animal observes the same action performed by another). If we understand the pain of others, and assume that they feel pain in the same way as us because of mirror neurons, we can't do the same with plants as we have different hormones and nervous systems etc . Thus it would be illogical to conclude that plants feel pain in the same way as us.


Plant neurobiology:

Auxin- is a hormone unique to plants which in charge of growth and plant behaviour. It stimulates the formation of vascular strands and roots. It also regulates vesicle trafficking and gene expression in roots.



Root apices are the "brain-like structure" of a plant. They're very sensetive to auxin and they are involved in lateral root formation (lateral roots are roots that extend from the primary root and anchor the plant to the ground- see picture on the left).

Plant synapses- Two adjecent cells which auxin and other chemicals are transported across. These synapses also play a part in immunology because they are the basis of cell-to-cell adhesions with other organisms (namely bacteria, viruses and so on). The cell-to-cell adhesions are also the active sites of the transport of molecules and metabolites.

And plant nerves:

Vascular strands: acts as a plant endoskeleton (something that holds the plant together) as well as the plant nerves. The leaves have single strands which combine to form the bundle of the stem and the vascular cylinder.

As for xylems and phloems, xylems are involved in the transmission of action-potential-driven electric signals (which cause short lasting events) and phloems are involved in the transmission of hydraulic signals (i.e. water-driven signals).

And root apices are, to quote:

Plant Brains: Each root apex harbours a unit of nervous system of plants. The number of root apices in the plant body is high and all brain-units are interconnected via vascular strands (plant nerves) with their polarly-transported auxin (plant neurotransmitter), to form a serial (parallel) nervous system of plants. The computational and informational capacity of this nervous system based on interconnected parallel units is predicted to be higher than that of the diffuse nervous system of lower animals, or the central nervous system of higher animals/humans.

So all of this concludes that plants do indeed have a nervous system, albeit not as complicated as that of animals. Then again, none of this has specified that plants feel pain, just that they can transfer hormones and electrical impulses. Until I find more conclusive evidence, I won't subscribe to the idea that plants do feel pain, but I do accept that they respond to stimuli.

NB: Obviously, none of this is mine. I've stolen everything from this website and reworded so that it's easier to understand. If you're interested in reading more about human pain and the mechanisms behind it, this website seems pretty interesting.

I think I'm going to follow up this post with another one about the ethical and philosophical implications for me if as a result of this research because I'm not sure about whether or not, in light of this, plants should have more of a moral status.


* Note that the existence and significance of mirror neurons is by no means definitive in humans, although it is generally accepted in monkeys so I'll just give the theory the benefit of the doubt.