I think it is a genuine question instead of a lame one. I even never ever thought about this before 😳

So far I can tell that your plants/flowers will absorb the water (including dissolved nutrients) to keep survive and fresh, if possible will undergo photosynthesis as well. But if your plants/flower are not aquatic organisms, their stem will soon get rotten. This case will change the water into a medium for another organisms to live e.g. algae, protozoa, etc. Then ‘higher’ organisms will take part when the environment support them, e.g. insects’ larvae, due tue adequate DO and nutrients produced by algae and another photosynthetic pioneers.