IIRC, trees release specific substances into their root systems in response to damage or illness in order to communicate to nearby trees. Dying trees will even give up their sugar reserves to feed younger, healthier trees.
So, while it may not be on the same level as animals, I can see an argument being made that trees respond to something resembling "pain" or "suffering".
I did a quick search and stumbled across this article[1] from the Smithsonian Magazine which corroborates some of this and expounds on it a bit. It waxes a bit... mystical, I guess? It does seem to be based on science, but the only thing it links to are books on the subject. So, you know, grain of salt. It's a place to start, though.
1: https://www.smithsonianmag.com/science-nature/the-whispering...
How about the line between "life that will likely suffer when prepared for us to eat" and "life that will likely not suffer when prepared for us to eat"?