It just came to my mind that that situation can happen.
I guess that lots of sci-fi stories tell about humans landing on some planets that flora would consist of plant-like beings.
Given that all of these 'beings' are coexisting together filling every step of ecosystem ladder (whatever it may be), then human 'invaders' would start living in such world.
Now, let's see what the outcome will be:
- at first humans must to adapt to new ecosystem and find what these 'plants' will consist of;
- second step would be identifying proper species that would serve as food and what it will be like to live on this kind of food;
- if we assume that previous step is sufficient for our humans to survive, they will live that way as long as this 'new food' would not harm them;
- as decades and centuries pass, human gastrointestinal tract would change and adapt to this new diet; planet's ecosystem would also change (in what way?) as there is a 'new player' in the game of life;
Of course, all of this can be possible and valid as an answer to Your question IF we would classify 'native plants' as plants. For human newcomers they may seem static, rooted to the ground, in various sizes, colors, scents. The way of reproducting can also be not-requiring other 'animalish' species (like bees for that matter). They don't need to be hunted down (they don't move), they do not defend themselves - these can impact on less-aggressive social behaviours in human community.
Simply put, I would say that in world given above humans may not need that effort of tooth-and-claw and therefore may result in smaller amount of physical aggression between people.