It's too early** to trawl the results of my internet search, so I'll give anecdotal evidence. But you're welcome to conduct your own search on the topic, and perhaps when I'm less hungover from last night's celebration*** I'll feel up to trawling (I wouldn't troll on something this important to me.)
Plants pick up on the emotive energy patterns of those around them. My boyfriend is going in for his Master Growers Certification, and he did some early projects on the subject.
Set up two grows identical in environment, gave identical sets of nutrients, identical light and dark patterns, identical temperature, humidity, feeding/watering times etc...
One crop was given love. No one not in a positive mood was allowed into their space, the were admired and given positive emotive energies during feeding and trimming.
The other crop was given anger. The only people in their enclosure were upset about something. They were yelled at, and belittled while being fed and trimmed.
The first crop had triple the yeald and double the quality of the second.
He has since expanded the positive energy experiments to include love making (not mear sexual encounters, as the actual act doesn't have much impact ether way, but the deeply connected emotive back and forth between a couple deeply committed to each other's happiness and well-being does a greenhouse good.)
Similar to the studies done showing that holding and cuddling premature babies increases their growth rate.
I connect more with trees than crops, (though I've seen for myself the difference between my boyfriends crops and the crops of his students who have picked up all the light-timeing and nutrient tracking, but haven't got their life together enough to control their emotive energies, or don't believe it makes a difference and don't bother to try.) so my "plants have emotions" encounters are less scientifically provable.
But there have been times in my life where I have been bombarded with the negative emotions of others, and in those times I find solace in connecting with trees. I'll walk till I find a tree that feels friendly or sympathetic, and if it's big I'll sit with my back to its trunk and reconnect with the vastness of time and space, loose all the energies that have stuck to me, then recapture my own essence and deal with whatever emotions are truly my own. Or if it's a little tree, I'll just reach my hand out and touch my palm and fingers to it, connecting with its upward reaching energies to uplift myself enough to deal with everything I've got going on -mine or not.
My own examples could be dismissed as placebo, using device to cycle myself into a particular mood or feeling. They are unprovable. I know. But they gave me a foundation to understand my boyfriends work from, and the beginnings of knowledge in how best to help him. I know to respect the emotional energy of his greenhouses, and am happy to go and admire his plants and give them positive energy, even if I'm not much help with taking care of them in the more physical aspects like feeding watering or trimming.
It didn't take much talking to get him to agree to have a similar emotive energy standard for our home. Negative feelings are delt with sooner rather than later, and positivity encouraged to flourish. Chaotic energy visitors are welcomed to the outdoor living spaces, but politely deflected from coming inside.
It's made coming home from work easier on both of us to know that we'll be (for the most part) coming home to a sanctuary. As well as deepening our relationship.
**5am
***my native status has been confirmed and the bureaucratic machine is one step closer to finishing the paperwork. I should have my card by January.