I like that at the end of the narrative example script it emphasises the power of the people to set things right, assuming "the people" is a guy with a magic plant gun, and "things" is the soil quality, but the message works. My main issue with the dialogue is that it's heavy handed, at least for the introduction. It seems to me like it's basically "this soil is bad" "that's because of humans", made into real dialogue, but not softened.
The demo is great. I'm not sure if there's a way to close the ammo screen without filling the cylinder (I'd recommend closing it with "R" again, and using just "E" to chamber), and it's not always clear what each seed does (which I'd recommend fixing with a tutorial or descriptions). I understand that this is obviously a demo, and these are likely just not implemented yet, but I have to bring it up.