It's more the processing that's relevant for pain. No processing, no pain.
For instance, some humans have very specific genetic mutations that do not allow them to feel pain. The peripheral nerves still send the pain signals to the brain but it cannot process them. Therefore, no pain.
There could be a discussion on whether very simple nervous systems (like in jellyfish) without a central component (brain) can process pain. But I'm not a biological researcher or philosopher so that's outside my Lemmy paygrade.
And what makes them different from any other chemical reaction is a little disingenuous. Might as well ask what's the difference between burning a human on a stake and melting glass? Both are just chemical reactions involving heat from a certain perspective.
There is simply no organ comparable to the brain in plants that would allow for plant pain. That's pretty much it.


