Plant's dont suffer any subjective pain and they are not able to think.

Trees don't suffer any subjective pain, nor are they able to think. They are not sentient.

"No I wouldn’t, but maybe that’s where I’m still limited in my own thinking! To me thinking and information processing are two different constructs. I have to be careful here since this is really bordering on the philosophical, but I think purposeful thinking necessitates a highly developed brain and autonoetic, or at least noetic, consciousness. Plants exhibit elements of anoetic consciousness which doesn’t include, in my understanding, the ability to think.  Just as a plant can’t suffer subjective pain in the absence of a brain, I also don’t think that it thinks."
http://www.scientificamerican.com/article.cfm?id=do-plants-think-daniel-chamovitz&page=3