Plant ethics is described like this:
[P]lant ethics is an open invitation to fine-tune our dietary practices in keeping with the philosophical and botanical considerations of what plants are, what they are capable of, and what our relation to them should be.
If you read the debate, I side with Gary Francione, who says:
If plants are not sentient—if they have no subjective awareness—then they have no interests. That is, they cannot desire, or want, or prefer anything. There is simply no reason to believe that plants have any level of perceptual awareness or any sort of mind that prefers, wants, or desires anything.
The discussion of our ethics of eating does not need to include plant ethics, and that is about the only time it ever gets brought up, because plants are not sentient and so do not need ethical consideration. That doesn’t mean that anything you do to plants is ethical, just that the plants themselves are not objects of moral consideration. We don’t smash people’s windows because we think the window is an object of moral concern but because damaging the window violates the rights of the home owner, who is an object of moral consideration. Similarly we don’t think mountains are sentient but we don’t just destroy them because of obligations to the rest of the world, both the human and non-human inhabitants of the present and future.
This is all being brought up because there is plenty of evidence that plants can react to stimuli. In my post on amazing plants I showed examples of plants moving when touched and catching prey. However there is no reason to believe that they are able to think or feel. All those actions can easily be performed unconsciously, and are.
There is also no known way for a plant to have thoughts. They do not have a nervous system, which is the only way we know for conciousness to exist. Animals have the same sort of nervous system as us but, more importantly, we have evidence of them thinking, planning and behaving in ways that mimic us. I’ll be addressing animal intelligence shortly as there have been a few articles around with some nice examples. Plants do not solve problems, they do not react emotionally and there is no reason to suspect that we just haven’t found that part of them yet.
If plants were sentient then they we would need to make sure we treat them ethically. Either we would have to say that as both plants and animals can suffer and we need food to survive we can eat anything or we would have to see how we could survive while causing the least harm to other sentient beings. But while that is an interesting mental exercise it just isn’t a practical concern that anyone needs to worry about. There just isn’t evidence that plants are sentient.