Well, on an episode of Mythbusters, they tested the possibility that plants feel pain/emotion by hooking one up to a polygraph (And then an EEG Machine). Then, they hit the plant, said mean things to the plant (Lol), and did other stuff - In the end, the plant didn't show any signs of pain.
Also, just to tell you my general opinion on animal rights:
I think that there is a fine line between hurting and killing animals to survive, and doing it for unnecessary things such as entertainment is ridiculous.
I read an article once about animal testing and how they test NAIL POLISH on bunnies by dripping it in its eyes, then giving it no medical treatment. That's not even a good test, because if that happened to a person, they wouldn't just leave it there! And nail polish, of all things, is not worth giving an animal a life of cruelty, plus, who drips nail polish directly in their eyes?
Now, on the other hand, testing, say, a pacemaker on a few animals. That's worth it, since the pacemaker will save many, many lives, however, the animal should be cared for - Let's say you test it on a dog. If the dog dies in the test, it dies. If the dog lives, it should be treated for any sickness or problem that it got from the test until it's healthy. Then, it should be set free - Given a home or something - NOT put back in a cage and tested again. If you are going to test an animal in any way, you should only do it once.
Yeah, that's just for animal testing...I'll get to my opinion on eating animals later.