Evidence for learning behaviors in plants is to my knowledge very scarce. […] a sunflower who’s stem grows on the shadier side and reset during the night in order to “track the sun”.

The learning behaviour is actually much more nuanced than that. This is one of the main papers on it (the Youtube video I linked earlier puts it in a more digestable format, plus provides some extra context from the main researcher’s talks and other papers).

Basically they took a plant which has a reaction to close its leaves when disturbed and repeatedly dropped its container a small distance, which caused the plant to close its leaves. After only a small number of repeated drops, the plants started reopening their leaves more quickly, and eventually stopped closing them entirely. However, the plants would still close their leaves as normal when a different stimulus of gently shaking their container was presented. They were also capable of remembering the learned behaviour of not closing when dropped for months at a time, and their capacity for learning depended on environmental conditions – when the plants were grown with less light, they learned more quickly.

In other words, it’s much more than a reflex. I would like to note that the “it’s just a reflex” argument doesn’t have a very good track record in general!

The same researcher, Stefano Mancuso, has many other fascinating plant intelligence experiments and is one of the pioneers of the field of plant neurobiology. The pea plant sensing experiment I mentioned earlier is also his work. It is still an emerging field, but the evidence is quite impressive. It also just makes sense when you think about it – there has been so much evolutionary benefit for sensing and learning behaviours in all other life down to the microscopic level that it would in fact be more surprising if similar behaviour didn’t exist in plants.

I don’t think anyone, including the authors, is honestly claiming it as incontrovertible evidence of plant sentience. Personally I think the main takeaway from it should be that learning, sensing etc. aren’t nearly as complicated of a behaviour as we used to think they are, and can likely occur without consciousness or sentience as we humans experience them.

It is somewhat arbitrary very the exact line is, but I don’t think there is much debate to be had that killing animals is unethical. There are very few people who wouldn’t react with horror at the idea of killing kittens and milking the mom dry but somehow for cows this is acceptable?

Yeah like I said, the ethical argument is easy for complex mammals. It’s simple animals where it’s hard. I think basically no one, including most vegans, would find any ethical issues with killing a parasitic worm, for example.

I don’t think it is possible to create a clear and objective definition of intelligence or sentience that excludes all plants (and mushrooms!) without excluding e.g. tardigrades, honeybees, silkworms, mealworms, snails, or indeed lobsters. We simply lack the metrics on which to base it. And I believe if we did have those metrics, we’d find that on them many plants indeed “outrank” many animals.

Even beyond the purely philosophical argument of defining a stronger foundation for veganism besides “is it in the kingdom Animalia”, this has actual practical relevance. Certain micronutrients that cannot be gained (or easily gained) from plants would be available in simple animals, which could make them a valuable food source in a world that doesn’t eat chickens, pigs or cows. Simple animals can also be valuable for bioengineering. Conventional non-food uses like silk production are also pretty nice.

We don’t know what consciousness requires to manifest (nor really even what it is), so ruling out plants having any level of consciousness just because they don’t have animal neurons is an opinion, not a fact. There are electrochemical signals happening within them, so it is entirely possible they perform similar functions to an animal nervous system without having any neurons.

Many animal behaviours could also be argued to be reactive. Particularly, if we reduce learning behaviours in plants to mere reactions, then by the same logic it could be argued that learning behaviours in simple animals (like, say, lobsters, which have 1/10th the number of neurons a cockroach does) are also just complex reactions.

I’m not saying this because I really believe plants are conscious or sentient (i.e. capable of sensing in a way analogous to humans or complex animals like, say, dogs or cows). I’m saying it to illustrate how with our present-day knowledge any moral line we draw is going to ultimately be arbitrary. Excluding complex mammals like cows or pigs from our diets for being too sentient is easy, but the simpler the animal becomes the harder it gets to create objective criteria that excludes, say, bugs, but doesn’t exclude any plants.

then being vegan is still the more moral option since the amount of plants that need to be “murdered” to feed an animal until it’s ready for slaughter is orders of magnitude higher than the nutritional value we get out of the animal when we murder it.

Correct, and this argument is the one you want to use with the average Lemmy user. Not because of the moral cost of killing plants or animals, but because of the environmental cost. Most Lemmy users already agree that climate change is a problem, so this argument is an easier sell to them. It is what made me reduce my consumption of meat.

That page is factually untrue and grossly uninformed of the fascinating things plants are capable of. Honestly expected better of vegans.

Most plants evidently feel pain given that they have a stress response to being damaged. Many of them, like the famous venus flytrap, can feel much more than that. Many plants are capable of sensing their surroundings and responding to stimulus – rice can sense the sound of rain and pea plants can see their surroundings to grow towards a nearby support (and yes, they are actually sensing photons, not just blindly reaching). Plants also communicate with one another; they can for example release defensive embittering or toxic chemicals as a response to nearby plants being predated on. They are even capable of learning.

Plants are capable of so much more active behaviour than we previously realized. On many of the metrics used by contemporary animal rights activists to define sentience, such as whether an animal is capable of sensing pain or learning, plants also qualify as sentient. The most complex plants are vastly more complex organisms than the simplest animals. Just because they’re alien to us and exist on a different timescale does not mean they aren’t sentient.

Great, then I don’t need to explain to you why your meme is daft.

Society at large has agreed murder is fine if the victim is tasty

Unless you’re a fruitarian you, too, have agreed that murder is fine as long as the victim is different enough from you. If you are a fruitarian you’re probably still fine with slavery and eugenics, given that most cultivated fruiting plants are farmed and selectively bred by humans.

Nature is an endless system of predation and consumption and humanity is not yet technically developed enough to transcend it. You physically cannot live without other living, sensing, feeling things dying.

You know Hitler was notoriously vegetarian?

I mean they were right.

Just a tip for the future, if you want to sell veganism to people, soapboxing under a FoodPorn post of some barbecued ribs trying to argue that the picture is gore is not an effective way of doing it.