Plants may not experience pain, but they are concious to the environment around them in more ways then just photosynthesis. They communicate not only among themselves but with animals as well.
Check out this link if you get a chance.
https://www.linkedin.com/pulse/communication-naturally-how-do-plants-animals-tim-clabon
Please excuse my forwardness, I don't wish to be offensive, but rather honest in our open dialoge.
I find that reasoning to be limited by knowledge that we hold on our hands. We learn so much everyday, and much of what we thought we knew, turns out to be entirely wrong.
I think there are things that may have yet to be discovered based on probability alone. I am excited by what we discover.
However, I think by not having a nervous system that does not make them unaware. I find it only reasonable to assume that all living organisms react to harmful inflictions based on ones subconscious will to survive.
Our "nervous system" is our specified layout for the transfer of data. Pain is only a description of our sensors transferring data to a motherboard. Not all organisms are built the same but all do respond to inflictions and almost every species on the world known so far communicates. Just because we don't understand their languages doesn't mean we can't see that it exists.
In fact here is another great article on the communication that occurs between bacteria.
https://www.ncbi.nlm.nih.gov/m/pubmed/16212498/
To communicate could suggest consiousness in all reality. Which would mean that, as I utilize a honey bee, you utilize beneficial bacteria that process the salts that feed our plants.
I presume that based on the idea that consiousness is the basis for the description of life. At least that is the argument for my description of life for why I support pro choice.