Reddit mentions of Other Minds: The Octopus, the Sea, and the Deep Origins of Consciousness

It depends on what you mean by 'sentient'.

Plants are capable of responding to their environment and to noxious stimuli. There is a sense in which they process information about their environment. But the same can be said of security cameras and thermometers. I don't think it is morally significant.

There is a another sense, which is having a conscious experience of one's environment. It's the difference between conscious and unconscious processing of one's environment, of there being something "it is like" to undergo an experience.

Because we cannot directly the experience the subjectivity of another being, we will never have incontrovertible proof that plants are not conscious in this sense. But we can reason indirectly about it, and make some informed guesses on the basis of observed plant behavior. We can take the experience of pain as an example, since it's the one that comes up most often in these discussions.

Pain has an adaptive function in animal organisms because animal organisms are capable of modulating complex behavior in response to it, and to prioritize the harmful stimuli over the many other kinds of stimuli their are receiving, often from many other sensory modalities.

Plants, by contrast, do not take in information from many different sensory modalities, and there is no evidence that they have a central way of integrating these various modalities into a single experience. There is no evidence they have anything like attention, which they can direct in different ways. They way in which they respond to threats from the environment is more akin to a mousetrap being set off; just as a mousetrap doesn't need to be conscious in order to function, I'd wager that a plant wouldn't really benefit from a conscious experience of pain, because there is no attention and decision-making (in a CNS, for example) that it might inform.

I'd recommend reading Other Minds for a nice account of the origins of consciousness. The author provides some compelling reasons for thinking that a nervous system is really central to its emergence.

Those creatures are amazing. Their branch on the tree of life separated from ours about 600 millions years ago. They evolved completely differently to the point they look as they are from another planet, yet they also developed eyes and a big distributed nervous system. Different organisms interestingly developing the same kind of tools/sensors and strategies to survive in different environments. Plus they are super smart. They can learn just by looking at other organisms ... and strangely can recognize human's faces.

They can shapeshift to look like a rocks or a venomous sea snake. They change color to match their environment ... although they are color blind. A theory is that they "see" with their eyes but perceive colours through their skin.

Please stop eating them :-)

I recommend this book : https://www.amazon.com/dp/0374537194/ref=cm_sw_em_r_mt_dp_U_jruJDb0DDD2D3

Or octopi.