Well, the Russians have been doing this sort of thing for decades. Does anyone recall Lyall Watson's 'Supernature'? So, fact from fantasy. It is entirely true that plants are sensitive to all sorts of environmental triggers (light, gravity, touch)...and there have been demonstrable and replicated studies which show seedlings which are stroked (around 30 strokes) do much better than those which are left alone. This is because they are responding to the touch - thigmatropism - and will direct cellular growth to thicken the stems. Wind, grazing animals will also do this. If you say 'nice plant- look at you in your lovely green life' as you do it, it will not have much effect...but the extra blast of carbon dioxide from your exhalation just might.
Recent research has shown that plants are far from solitary organisms but exist in a network of interlinked soil micro-organisms (such as mycorrhizae)...trees can, for example, isolate an ailing limb by cutting off nutrient supply (leading to loss) or, can deliver nutrient packages to an ailing tree in the same affiliated group.
In brief, the natural world is stranger and more complex than we might have initially imagined...but this can also offer up a template for all sorts of woo.