When you expose plants to air, they are little bit like a sponge, internally, (anatomically, aquatic plants are hollow mostly, search aerenchyma). These will get filled fairly rapidly.
Then take a sponge and place into the water, it'll pearl as well.
Water changes are good also because the sticky micro bubbles stick to algae cells also, and pull them off plants.
Still, we can tell between growth and pearling alone.
I always get better growth and health the day of a water change, some have done daily good sized water changes and dosed etc with excellent results, but that's a lot of work.