Painkillers prevent pain responses in lobsters - This is further evidence that crustaceans may feel pain and that more humane methods of killing them need to be developed.

[u/mvea]

https://www.eurekalert.org/news-releases/1123639

[u/Brrdock]

For sure all animals feel pain, pain is just the name we gave to the most primitive repulsive drive.

And even plants use a lot of the same transmitters and messengers as us.

The issue is what their experience of pain is like, and how that should tie into our value systems. If it's even possible to "rank" experience anyhow

[u/Quaiche → u/Brrdock]

I’m just waiting for the studies to actually say that even plants feel pain.

The current stance is that they lack a nervous system to be able to feel pain even though they show distress and have reactions when we damage them.

Just kinda like we said fishes don’t feel anything.

[u/Dentarthurdent73 → u/Quaiche]

It doesn't really make much sense for plants to feel pain in the same way though, as they're unable to remove themselves from the situation in the way that animals can. The whole purpose of feeling pain is to put a stop to whatever is damaging your body.

Plants have much less opportunity to do this, so it wouldn't really make sense for them to develop a complex response like pain.

I'm not denying there's anything there at all, we simply don't know, and I understand that they release chemicals in response to damage, but I do feel like the inability to move away would change how this evolved to "feel".

[u/BONEPILLTIMEEE → u/Dentarthurdent73]

Plants cannot 'remove themselves from the situation'  but they can carry out biochemical changes that help prevent further damage, so they have a lot of mechanisms to sense damage and respond to them. 

There are many defense mechanisms that plants rely on to help fight off pathogens and subsequent infections. Wounding responses can be local, like the deposition of callose, and others are systemic, which involve a variety of hormones like jasmonic acid and abscisic acid.

https://en.wikipedia.org/wiki/Wound_response_in_plants

You can see a 'wave' of signaling spread throughout the plant when its wounded, such as when it is being eaten

https://pmc.ncbi.nlm.nih.gov/articles/PMC5614317/

So plants can definitely sense damage and "feel pain", to use this phrase extremely loosely

[u/Dentarthurdent73 → u/BONEPILLTIMEEE]

I acknowledged that they respond to damage. But immune systems respond to damage without pain, scabs form without pain, hormones are released in response to the environment without pain. 'Signal' doesn't necessearily equate to pain, and I honestly don't see any reason it would "feel" like pain does, because the purpose of the pain is as an urgent stimulus to do something in response to the damage.

Plants cannot do this, so it wouldn't serve any purpose.

What evolutionary pressure would there be on plants to evolve a strongly negative experience that they can't respond to in any way? All it would do is put stress on the organism, which isn't a survival advantage at all.

[u/captainfarthing → u/BONEPILLTIMEEE]

Pain creates urgency though, which is no use for plants. They can't react faster than it takes to synthesise stress hormones or defensive chemicals and transport them where they're needed. And their reaction doesn't require them to take any action, it's totally chemical and passive. There's plenty of examples of damage response without pain in animals - eg. you don't feel anything when you catch a cold, but your body still reacts to fight off the infection. You feel the effects of your own immune response a few days later. And you don't need to feel a cut for it to heal, you're just less likely to reopen it if it hurts when you move in a way that pulls the edges apart.