Do plants feel stressed? Well, yes and no. Actually I’m not going to tell you that they don’t feel stress in ways similar to humans. There have been some studies where plants have had leaves hooked up to electrodes and then were pruned and there was evidence that they reacted.
There is also evidence that a plant under attack from an insect sends chemical signals to its neighbors. Is that stress? Is it a warning? We’re not quite sure.
But there’s this. Here’s a healthy, normal looking zygocactus (otherwise known as a non-blooming Christmas cactus).
Occasionally they look like this. This is what happens when they get too near a window (in other words, get chilled by glass–at least in my climate).
And there’s this, which is what happens if they’re getting too much sunlight.
Are they stressed? Somewhat, but not so much that they might be overly susceptible to insects or disease (which is what happens when a plant is stressed).
And then there’s this. This probably doesn’t look all that odd to you, because these zygo cactus can bloom randomly throughout the year.
But this is ‘Holiday Cheer’ the first of the plants to bloom for me. It bloomed for me last October. I remember posting a photo with it’s tag and the rather snarky comment “what holiday?”
I would say that it’s the Columbus Day/Easter cactus but Easter cacti are an entirely different genus!
Gardendaze 
It is not all that philosophical. Plants do ‘feel’ stress. The difference between how they feel stress and how we do is not all that complicated. The main perceived difference is merely the thought that goes into it. The stress that we feel starts out as a basic reaction to what causes stress. We engage in all sorts of reactions to stress that we are not even aware of. For example, the way the body regulates temperature, and adjusts to sudden changes of temperature, is something that initially happens automatically, without thought. We do not think about it until we want to remove or apply more clothing, or put another log on the fire.
I remember the old television show “In Search Of” in which the cabbage started screaming while connected to the machine that monitored neural impulses. It was disturbing!
I thought that I had seen some things like that a long time ago as well but my memory isn’t quite as good as yours–either that, or I was so troubled, I just blotted the whole thing out completely so that I can still prune when necessary.
I know that occasionally when I am trimming a house plant, I will say something silly to it like, “now I know this is going to hurt now, but I really have to do it. It’s going to make it so much better later on.” Does it matter? Who knows? At least I feel better.
Karla