Neuroscientist Greg Gage
If you have one of those annoying Vegan/Buddhist friends who keep yammering about how they don't eat meat because "animals have a mind of their own", show them this video of Neuroscientist Greg Gage demonstrating many of the 'sentient' properties of plants, just to piss them off:


Granted, Gage's arguments about the 'intelligence' of plants are explained through electrochemistry, hence they are deeply rooted (no pun intended) in material Science. "Plants don't get depressed" he mentions, which would probably be objected by MANY proud plant owners who swear by the benefits of talking in a nice tone of voice to their beloved leafy children while watering them. What we know for certain is that plants do have the ability to feel pain, detect the presence of predators AND even alert other neighboring plants about nearby dangers - all that without a need for Twitter or a Facebook account...

And there's that ground-breaking - hence highly controversial - book The Secret Life of Plants which described experiments attempting to prove whether plants could respond to music or even 'feel' whether they were going to be hurt by the experimenters.

Stuart P. Hameroff M.D., who's been argumenting about the involvement of 'micro-tubules' in the cell structure for the 'emergence' of Consciousness through quantum physics - yet another controversial idea - points out how a paramecium is a single-celled organism devoid of a brain, yet it's capable of moving through water searching for food, detect light and other attributes shared by 'brained beings'. You can listen to Hameroff discuss these ideas with Dr. Jeffrey Mishlove in this episode of New Thinking Allowed:


The point is that as we learn more about the abilities of 'lower' forms of life, we keep expanding our interpretations about what exactly constitutes Life and Intelligence - could we, for example, recognize an extraterrestrial life form whose chemistry is not based on Carbon, like ours is? - and we may sooner or later realize not having a brain does not necessarily mean being devoid of Consciousness. A plant may not share the same consciousness as a bear or a human being, but that doesn't mean we wouldn't be able to 'communicate' with them in some form.

Maybe if we did, we would eventually realize we monkeys only think we're running things