Plants certainly don't feel pain, nor can they think. However, plants do react to damage - they have various systemic responses to harm, including chemical processes and whatnot. There are some that react by releasing unpleasant-tasting toxins into their leaves, and then 'communicate' a warning to their neighbours with airborne chemical signals. They react to damage, and then try to protect themselves - in animals, those responses would be considered 'suffering' and 'self-preservation'.

Not sure where I'm going with this. I'm definitely not arguing for 'plant rights' or 'tree sentience' or anything. I guess I'm just responding to the notion that 'plants don't feel anything so we can do what we want to them without moral compunctions'. They sure don't 'suffer' in a way we can relate to, but arguably they do experience a kind of suffering.

Perhaps the technology is near that'll allow us to synthesise a nutritionally perfect food, using no animal or plant products but providing a completely balanced diet. That'd be cool, and depending on the production costs and energy demands, it could be a great move in environmental terms too. But unless or until such a food is developed, the continued harvesting of animals and plants remains a necessity.