I remember reading that some species of plants release a specific chemical or audio frequency (I can't remember which) in response to being cut down, and this chemical is detected by other nearby plants that cause them to become stiffer or something along those lines. Whether that meana the plants feel pain or not, there isn't anything conclusive. I think it would be pretty hard to feel pain without a nervous system, but its possible that what constitutes pain doesn't need a nervous system or pain receptors at all. Im not a scientific expert, I just tried to be funny.